Image encoding method, image decoding method, image encoding apparatus, and image decoding apparatus

ABSTRACT

An image encoding method includes: determining respective decoding times of a plurality of pictures included in a motion picture such that decoding times of a plurality of lower layer picture which do not belong to a highest layer of a plurality of layers are spaced at regular intervals, and decoding timing for each of the plurality of lower layer pictures is identical between a case where the plurality of encoded pictures included in the motion picture are decoded and a case where only the plurality of lower layer pictures are decoded, encoding each of the plurality of pictures included in the motion picture in accordance with the encoding order according to the determined respective decoding times, and generating an encoded stream including the plurality of encoded pictures and the determined respective decoding times for the plurality of pictures.

BACKGROUND

1. Technical Field

The present disclosure relates to an image encoding method forperforming hierarchical encoding of an image, an image decoding methodfor decoding an image subjected to the hierarchical encoding, and thelike.

2. Description of the Related Art

Conventionally, there have been suggested an image encoding method forperforming hierarchical encoding of an image and an image decodingmethod for decoding an encoded image subjected to the hierarchicalencoding (for example, see NPL 1).

CITATION LIST Non Patent Literature

-   NPL 1: Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T    SG16 WP3 and ISO/IEC JTC1/SC29/WG11 12th Meeting: Geneva, CH, 14-23    Jan. 2013 JCTVC-L1003_v34.doc, High Efficiency Video Coding (HEVC)    text specification draft 10 (for FDIS & Last Call)    http://phenix.it-sudparis.eu/jct/doc_end_user/documents/12_Geneva/wg11/JCTVC-L1003-v34.zip

SUMMARY

In one general aspect, the techniques disclosed here feature an imageencoding method for encoding a motion picture for each picture whichbelongs to any one of a plurality of layers, without referring toanother picture which belongs to a layer higher than the layer to whichthe picture belongs, the image encoding method including: determiningrespective decoding times of a plurality of pictures included in themotion picture such that decoding times of a plurality of lower layerpictures which are a portion of the plurality of pictures included inthe motion picture and which do not belong to a highest layer of theplurality of layers are spaced at regular intervals, and that decodingtiming for each of the plurality of lower layer pictures is identicalbetween a case where the plurality of pictures included in the motionpicture which has been encoded are decoded and a case where only theplurality of lower layer pictures are decoded; encoding each of theplurality of pictures included in the motion picture in accordance withan encoding order according to the determined respective decoding times;and generating an encoded stream including the plurality of encodedpictures and the determined respective decoding times for the pluralityof pictures.

The image encoding method and the image decoding method according to thepresent disclosure can suppress the processing load.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram illustrating an example for realizing temporalscalability with HEVC;

FIG. 1B is a diagram illustrating another example for realizing temporalscalability with HEVC;

FIG. 2 is a diagram for explaining a problem in that an encoded streamof 120 fps cannot be decoded;

FIG. 3 is a diagram for explaining an image encoding apparatus accordingto a first exemplary embodiment;

FIG. 4 is a diagram illustrating an example of encoding a motion pictureby using three layers according to the first exemplary embodiment;

FIG. 5 is a diagram illustrating an example of encoding a motion pictureby using four layers according to the first exemplary embodiment;

FIG. 6 is a diagram illustrating another example of encoding a motionpicture by using three layers according to the first exemplaryembodiment;

FIG. 7 is a diagram for explaining an image decoding apparatus accordingto the first exemplary embodiment;

FIG. 8 is a diagram illustrating decoding order and display order ofpictures and DTS (Decoding Time Stamp) and PTS (Presentation Time Stamp)of pictures when the encoded stream is reproduced at 120 fps accordingto the first exemplary embodiment;

FIG. 9 is a block diagram illustrating a configuration of an imagedecoding apparatus according to a first modification of the firstexemplary embodiment;

FIG. 10 is a flowchart illustrating an example of operation in which theimage decoding apparatus according to the first modification of thefirst exemplary embodiment decodes pictures in all the layers;

FIG. 11 is a diagram illustrating an example of changing DTS accordingto a second modification of the first exemplary embodiment;

FIG. 12 is a diagram for explaining pictures decoded in an open endrandom access unit according to a third modification of the firstexemplary embodiment;

FIG. 13 is a flowchart illustrating an example of operation in which animage decoding apparatus according to the third modification of thefirst exemplary embodiment decodes a motion picture on the basis ofauxiliary information for reproduction control;

FIG. 14 is a diagram illustrating an example of a conversion of DTS orPTS according to a fourth modification of the first exemplaryembodiment;

FIG. 15A is a block diagram illustrating an image encoding apparatusaccording to an aspect of the present disclosure;

FIG. 15B is a flowchart illustrating an image encoding method accordingto an aspect of the present disclosure;

FIG. 15C is a block diagram illustrating an image decoding apparatusaccording to an aspect of the present disclosure;

FIG. 15D is a flowchart illustrating an image decoding method accordingto an aspect of the present disclosure;

FIG. 16 is a diagram illustrating an entire configuration of a contentproviding system that implements content distribution services;

FIG. 17 is a diagram illustrating an entire configuration of a digitalbroadcasting system;

FIG. 18 is a block diagram illustrating an example of a configuration ofa television set;

FIG. 19 is a block diagram illustrating an example of a configuration ofan information reproducing/recording unit that reads information fromand writes information to a recording medium which is an optical disk;

FIG. 20 is a diagram illustrating an example of a structure of arecording medium which is an optical disk;

FIG. 21A is a diagram illustrating an example of a mobile phone;

FIG. 21B is a block diagram illustrating an example of a configurationof the mobile phone;

FIG. 22 is a diagram illustrating a configuration of multiplexed data;

FIG. 23 is a diagram schematically illustrating how individual streamsare multiplexed into multiplexed data;

FIG. 24 is a diagram illustrating how a video stream is stored in a PES(Packetized Elementary Stream) packet sequence in a more detailedmanner;

FIG. 25 is a diagram illustrating structures of a TS (Transport Stream)packet and a source packet in multiplexed data;

FIG. 26 is a diagram illustrating a data configuration of a PMT (ProgramMap Table);

FIG. 27 is a diagram illustrating an internal configuration ofmultiplexed data information;

FIG. 28 is a diagram illustrating an internal configuration of streamattribute information;

FIG. 29 is a diagram illustrating steps of identifying video data;

FIG. 30 is a block diagram illustrating an example of a configuration anintegrated circuit that implements a motion picture encoding method anda motion picture decoding method according to each of the exemplaryembodiments;

FIG. 31 is a diagram illustrating a configuration for switching adriving frequency;

FIG. 32 is a diagram illustrating steps of identifying video data andswitching a driving frequency;

FIG. 33 is a diagram illustrating an example of a lookup table in whicha standard of video data and a driving frequency are associated witheach other;

FIG. 34A is a diagram illustrating an example of a configuration forsharing a module of a signal processor; and

FIG. 34B is a diagram illustrating another example of a configurationfor sharing a module of a signal processor.

DETAILED DESCRIPTION

(Findings Forming a Basis of the Present Disclosure)

The inventor of the present application has found that the followingproblems occur in association with NPL 1 described in the “2.Description of the Related Art” section.

In an encoding method such as MPEG-4 AVC (Moving Picture ExpertsGroup-4Advanced Video Coding) or HEVC (High Efficiency Video Coding),scalability in a temporal direction (hereinafter referred to as temporalscalability) can be realized by hierarchically encoding pictures. Forexample, when all the pictures are decoded, the pictures can bereproduced at 120 fps, and when only pictures which belong to aparticular layer are decoded, the pictures can be reproduced at 60 fps.

By using such temporal scalability, double speed reproduction bydecoding only the pictures which belong to the particular layer at aninterval of 120 fps can be realized. Further, in a reproductionapparatus that does not support decoding at an interval of 120 fps(hereinafter referred to as 120 fps non-supporting reproductionapparatus), an encoded stream of 120 fps can be possibly reproduced at60 fps.

FIGS. 1A and 1B are diagrams each illustrating an example for realizingtemporal scalability with HEVC. In FIGS. 1A and 1B, a referencerelationship between layers and the decoding order (that is, encodingorder) of the pictures are illustrated.

FIG. 1A illustrates an example of encoding each picture with a threelayer structure. In FIG. 1A, TId is a Temporal ID and denotes anidentifier for identifying the layer. Herein, I denotes an I picture(intra-screen prediction picture), P denotes a P picture (for example,forward reference prediction picture), and B denotes a B picture (forexample, bidirectional reference prediction picture). A number attachedto the right of each of I, P, and B denotes display order of each of theI, P, and B pictures. An arrow indicates a reference relationshipbetween pictures. For example, picture B2 refers to picture I0 andpicture P4. More specifically, in a reference relationship between thelayers, the picture is encoded without referring to any picture whichbelongs to a layer higher than the layer to which the picture inquestion belongs. Instead, the picture is encoded by referring a picturewhich belongs to the same layer as the layer to which the picture inquestion belongs, or a picture which belongs to a layer lower than thelayer to which the picture in question belongs. Here, when pictureswhich belong to any one of all the layers with Temporal IDs of 0 to 2are decoded, a frame rate is 120 fps. In this case, when pictures whichbelong to any one of the layers with Temporal IDs of 0 and 1 aredecoded, a frame rate is 60 fps.

FIG. 1B illustrates an example of encoding each picture with four layerstructure. In this case, when the pictures which belong to any one ofall the layers with Temporal IDs of 0 to 3 are decoded, a frame rate is120 fps. In this case also, when the pictures which belong to any one ofthe layers with Temporal IDs of 0 to 2 are decoded, a frame rate is 60fps.

As described above, the 120 fps non-supporting reproduction apparatuscan possibly realize reproduction of 60 fps by using temporalscalability, and more specifically, the 120 fps non-supportingreproduction apparatus can possibly realize reproduction of 60 fps bydecoding only the pictures which belong to some of the layers of the 120fps encoded stream.

However, even in this case, the 120 fps non-supporting reproductionapparatus may have to decode the pictures at an interval shorter than1/60 seconds in some cases. Thus, there is a problem in that even if the120 fps non-supporting reproduction apparatus uses the temporalscalability, the 120 fps non-supporting reproduction apparatus is unableto decode the 120 fps encoded stream because the interval betweenpictures that are decoded is short.

FIG. 2 is a diagram for explaining a problem in that the 120 fpsnon-supporting reproduction apparatus is unable to decode 120 fpsencoded stream. The encoded stream as illustrated in FIG. 2 is the 120fps encoded stream as illustrated in FIG. 1A. In a case where the 120fps non-supporting reproduction apparatus reproduces the encoded streamat 60 fps, the 120 fps non-supporting reproduction apparatus decodesonly each picture which belongs to the layer with Temporal ID of 0 andeach picture which belongs to the layer with Temporal ID of 1.

In FIG. 2, T corresponds to a time corresponding to 120 fps, that is,1/120 seconds. When broadcasting content and accumulated content aredisplayed at a fixed frame rate, the decoding is generally performed ata fixed frame rate. Therefore, at the time of the reproduction of 120fps, both of the interval between the pictures that are decoded(hereinafter referred to as a decoding interval) and the interval duringwhich each picture is displayed (hereinafter referred to as a displayinterval) are T.

Therefore, even during the reproduction of 60 fps, both of the decodinginterval and the display interval need to be the time corresponding to60 fps, and more specifically, both of the decoding interval and thedisplay interval need to be an interval of 2T. However, as illustratedin FIG. 2, in a case where the reproduction is performed at 60 fps, adecoding interval between Picture I0 and picture P4 or a decodinginterval between picture P4 and picture B2 is T. There is a problem inthat the 120 fps non-supporting reproduction apparatus which requires atime of 2T as the decoding interval fails to catch up with the decodingof the pictures. More specifically, there is a problem in that theprocessing load is high in the 120 fps non-supporting reproductionapparatus.

In order to solve such problems, an image encoding method according toone aspect of the present disclosure is an image encoding method forencoding a motion picture for each picture which belongs to any one of aplurality of layers, without referring to another picture which belongsto a layer higher than the layer which the picture in question belongs,the image encoding method including: determining decoding times of aplurality of pictures included in the motion picture such that decodingtimes of a plurality of lower layer pictures which are some pictures ofthe plurality of pictures included in the motion picture and which donot belong to a highest layer of the plurality of layers are spaced atregular intervals, and that timing for decoding each of the plurality oflower layer pictures is caused to be identical between a case where aplurality of pictures included in the motion picture which has beenencoded are decoded and a case where only the plurality of lower layerpictures of the plurality of pictures are decoded; encoding each of theplurality of pictures included in the motion picture in accordance withencoding order according to the decoding times thus determined; andgenerating an encoded stream including the plurality of encoded picturesand decoding times that are determined for the plurality of pictures.

Accordingly, each of the plurality of pictures included in the encodedstream is encoded without referring to another picture which belongs toa layer higher than the layer which the picture in question belongs.Therefore, the image decoding apparatus can decode only the plurality oflower layer pictures in the encoded stream. The decoding times of theplurality of lower layer pictures included in the encoded stream arespaced at regular intervals. Therefore, when the image decodingapparatus decodes only the plurality of lower layer pictures in theencoded stream, the image decoding apparatus can decode these lowerlayer pictures in order at every lapse of regular interval of time.Therefore, by setting the regular interval to an appropriate time, theprocessing load of the image decoding apparatus can be alleviated. Morespecifically, the image decoding apparatus can perform decoding at aframe rate according to the processing performance of the image decodingapparatus without performing decoding of each picture at a high framerate. Further, timing for decoding each of the plurality of lower layerpictures is identical between the case where the plurality of picturesincluded in the encoded stream (for example, all the pictures) aredecoded and the case where only the plurality of lower layer pictures ofthe plurality of pictures are decoded. Therefore, the image decodingapparatus does not need to change the timing for decoding each of theplurality of lower layer pictures between the case where all thepictures of the encoded stream are decoded and the case where only theplurality of lower layer pictures are decoded. Therefore, the processingload of the image decoding apparatus can be further alleviated.

In the determining of the decoding time, a decoding time of each of aplurality of uppermost layer pictures which are some pictures of theplurality of pictures included in the motion picture and which belong tothe highest layer may be determined to be between the decoding times ofthe plurality of lower layer pictures.

Therefore, when the encoded stream is decoded, the uppermost layerpicture and the lower layer picture are alternately decoded. Therefore,any interval of the time for decoding each of the plurality of lowerlayer pictures in the encoded stream is longer than the interval of thetime for decoding each of all the pictures of the decoded stream. As aresult, the image decoding apparatus can decode each picture at a surelylower frame rate when the image decoding apparatus decodes only theplurality of lower layer pictures than when the image decoding apparatusdecodes each of all the pictures in the decoded stream. Therefore, theprocessing load of the image decoding apparatus can be reliablyalleviated

In the determining of the decoding time, the decoding time of each ofthe plurality of pictures included in the motion picture may bedetermined such that twice the time of the interval of decoding times ofan uppermost layer picture and a lower layer picture which are of theplurality of uppermost layer pictures and the plurality of lower layerpictures and which are continuous in decoding order is equal to theregular interval of time.

Therefore, any interval of the decoding time of each of the plurality oflower layer pictures is the interval of the decoding time of each of anuppermost layer picture and a lower layer picture which are continuousin the decoding order, and more specifically, any interval of thedecoding time of each of the plurality of lower layer pictures is twicethe interval of the time for decoding each of all the pictures in thedecoded stream. Therefore, in a case where a frame rate for decoding anddisplaying all the pictures of the encoded stream is 120 fps, the imagedecoding apparatus can decode each of the plurality of lower layerpictures included in the encoded stream at a time interval of areciprocal of a frame rate of 60 fps without any load.

In a case where the motion picture includes a plurality of random accessunits including a plurality of pictures which are continuous in thedecoding order, in the determining of the decoding time, the decodingtime of each picture in each of the random access units may bedetermined for each of the random access units, such that, in each ofthe random access units, all the pictures except a picture displayed, indisplay order, before a picture at a head in decoding order can bedecoded without referring to a picture included in another random accessunit. For example, the picture at the head is an I picture in which apicture that is after the leading picture in decoding order isprohibited from referring to a picture that is before the leadingpicture in the decoding order. Alternatively, the leading picture is anI picture in which a picture that is after the leading picture in thedecoding order and is before the leading picture in the display order ispermitted to refer to a picture that is before the leading picture inthe decoding order.

Therefore, for each of the random access units, the image decodingapparatus can appropriately decode each of the plurality of picturesincluded in the random access unit.

In the determining of the decoding time, in a case where a frame rate atwhich all the pictures included in the encoded motion picture aredecoded and displayed is f, the decoding time of each of all thepictures may be determined such that the decoding time of each of theplurality of lower layer pictures included in all the pictures is spacedapart by a time indicated by n times (n is an integer equal to or morethan 2) a reciprocal of the f.

Therefore, the image decoding apparatus can decode each of the pluralityof lower layer pictures at a time interval which is n times a reciprocalof that frame rate in order without any load.

The image encoding method may further include incorporating, into theencoded stream, display delay information indicating a display delaywhich is a time between a decoding time of a picture at a head indecoding order included in the motion picture and a display time of thepicture at a head in display order included in the motion picture.

Therefore, the image decoding apparatus can obtain the display delayinformation from the encoded stream. Therefore, when the image decodingapparatus starts decoding the encoded stream from a time before thedisplay start time by the display delay indicated by the display delayinformation, the image decoding apparatus can display the motion picturewithout delay from the display start time.

The image encoding method may further include incorporating, into theencoded stream, non-regular interval information indicating that thedecoding times determined for the plurality of pictures included in themotion picture are not spaced at regular intervals.

Therefore, the image decoding apparatus can obtain the non-regularinterval information from the encoded stream. Therefore, the imagedecoding apparatus can determine that each of the plurality of picturesincluded in the encoded stream cannot be decoded in order at the framerate of the display. As a result, while the image decoding apparatusrefers to the decoding time determined for each of the plurality ofpictures included in the encoded stream, the image decoding apparatuscan decode the plurality of pictures at appropriate timing.

An image decoding apparatus according to an aspect of the presentdisclosure is an image decoding method for decoding an encoded streamincluding a motion picture encoded for each picture which belongs to anyone of a plurality of layers, without referring to another picture whichbelongs to a layer higher than the layer which the picture in questionbelongs, the image decoding method including: obtaining, from theencoded stream, decoding times of the plurality of pictures included inthe encoded stream that are determined such that decoding times of aplurality of lower layer pictures which are some pictures of theplurality of pictures included in the encoded stream and which do notbelong to a highest layer of the plurality of layers are spaced atregular intervals, and that timing for decoding each of the plurality oflower layer pictures is caused to be identical between a case where theplurality of pictures included in the encoded stream are decoded and acase where only the plurality of lower layer pictures of the pluralityof pictures are decoded; and decoding each of the plurality of picturesincluded in the encoded stream or the plurality of lower layer picturesin accordance with the obtained decoding times.

Accordingly, each of the plurality of pictures included in the encodedstream is encoded without referring to another picture which belongs toa layer higher than the layer which the picture in question belongs.Therefore, image decoding apparatus can decode only the plurality oflower layer pictures in the encoded stream. The decoding times of theplurality of lower layer pictures included in the encoded stream arespaced at the regular intervals. Therefore, when image decodingapparatus decodes only the plurality of lower layer pictures in theencoded stream, image decoding apparatus can decode the lower layerpictures in order at every lapse of regular interval of time. Therefore,when the regular interval is an appropriate time, the processing load ofimage decoding apparatus can be alleviated. More specifically, imagedecoding apparatus can perform decoding at a frame rate according to theprocessing performance of image decoding apparatus without performingdecoding of each picture at a high frame rate. Further, timing fordecoding each of the plurality of lower layer pictures is identicalbetween the case where the plurality of pictures included in the encodedstream (for example, all the pictures) are decoded and the case whereonly the plurality of lower layer pictures of the plurality of picturesare decoded. Therefore, image decoding apparatus does not need to changethe timing for decoding each of the plurality of lower layer picturesbetween the case where all the pictures of the encoded stream aredecoded and the case where only the plurality of lower layer picturesare decoded. Therefore, the processing load of image decoding apparatuscan be further alleviated.

The image decoding method may further include changing the decoding timeof each of the plurality of pictures to have the regular interval in acase where decoding times of the plurality of pictures included in theencoded stream are not spaced at regular intervals; and in the decodingof the encoded stream, decoding each of the plurality of picturesincluded in the encoded stream or the plurality of lower layer picturesin accordance with the changed decoding time.

Accordingly, for example, the decoding time of each of the plurality ofpictures is changed to have the regular interval, and therefore, imagedecoding apparatus can decode each of the plurality of pictures includedin the encoded stream at every lapse of regular interval of time.Therefore, the processing load of image decoding apparatus can befurther alleviated.

In the decoding of the encoded stream, a determination is made, for eachpicture included in the encoded stream, as to whether the decoding timeobtained for the picture matches generation timing at which a processingsignal is generated at a cycle defined in advance, and when the decodingtime is determined to match the generation timing, the picture may bedecoded. For example, the image decoding method may further includedetermining a reciprocal of a frame rate at which all the picturesincluded in the encoded stream are decoded and displayed to be the cycledefined in advance.

Therefore, even if the decoding times of the plurality of pictures arenot spaced at regular intervals, each of the plurality of pictures canbe decoded appropriately at the decoding time of the picture.

It should be noted that these general or specific aspects may beimplemented using a system, a method, an integrated circuit, a computerprogram, or a computer-readable recording medium such as a CD-ROM(Compact Disc-Read Only Memory), or using any given combination of asystem, a method, an integrated circuit, a computer program, and acomputer-readable recording medium.

Hereinafter, exemplary embodiments will be explained in a specificmanner with reference to the drawings.

It should be noted that all the exemplary embodiments explained belowillustrate comprehensive or specific examples. Numerical values, shapes,materials, constituent elements, disposition positions and connectionforms of the constituent elements, steps, the order of the steps, andthe like which are shown in the following exemplary embodiments are onlyexamples, and are not intended to limit the present disclosure.Constituent elements in the following exemplary embodiments that are notdescribed in independent claims indicating the broadest concept areexplained as optional constituent elements.

First Exemplary Embodiment

FIG. 3 is a diagram for explaining an image encoding apparatus accordingto the present exemplary embodiment.

Image encoding apparatus 10 in the present exemplary embodiment obtainsa motion picture at a frame rate of 120 fps, and encodes the motionpicture, thus generating and outputting an encoded stream. In a casewhere all the pictures included in this encoded stream are decoded, themotion picture is displayed at a frame rate of 120 fps. In a case wheresome of the plurality of pictures included in this encoded stream aredecoded, the motion picture is displayed at a frame rate of 60 fps. Forexample, some of the plurality of pictures included in the encodedstream are a plurality of pictures each of which belongs to one oflayers other than the highest layer.

FIG. 4 is a diagram illustrating an example of encoding a motion pictureby using three layers according to the present exemplary embodiment.Image encoding apparatus 10 according to the present exemplaryembodiment generates 120 fps encoded stream by encoding a motion pictureon the basis of a prediction structure similar to the predictionstructure of the picture as illustrated in FIG. 1A. At this occasion,image encoding apparatus 10 adjusts a decoding time (DTS: Decoding TimeStamp) of pictures that are decoded only during reproduction at 120 fpssuch that the decoding interval at which the encoded stream isreproduced at 60 fps becomes 2T ( 1/60 seconds). More specifically,image encoding apparatus 10 adjusts the DTS of the plurality of pictureswhich belong to the highest layer of the plurality of layers.

FIG. 5 is a diagram illustrating an example of encoding a motion pictureby using four layers according to the present exemplary embodiment.Image encoding apparatus 10 according to the present exemplaryembodiment generates 120 fps encoded stream by encoding a motion pictureon the basis of a prediction structure similar to the predictionstructure of the picture as illustrated in FIG. 1B. At this occasion,image encoding apparatus 10 adjusts a decoding time of pictures that aredecoded only during reproduction at 120 fps such that the decodinginterval at which the encoded stream is reproduced at 60 fps becomes 2T( 1/60 seconds).

At this occasion, when the motion picture is encoded, a random accessunit called GOP (Group Of Pictures) and the like is configured so as toallow decoding to be started from any given picture of the encodedstream. In a random access unit, a leading picture in the decoding orderis a random access point. For example, as illustrated in FIG. 4, pictureI0 to picture B9 are a first random access unit, and picture I16 is ahead picture of a second random access unit. In this case, in the secondrandom access unit, a picture such as picture B11 does not refer topicture I16 or pictures subsequent to picture I16 in the decoding order,but is included in the second random access unit.

In a recording an encoded stream that is broadcast (that is, broadcaststream) and the like, a random access unit such as the first randomaccess unit may be recorded to the end of the random access unit. Atthis occasion, although picture P12 can be decoded, picture B11 isincluded in the second random access unit and is therefore unable to bedecoded. Therefore, operation during decoding would be complicated.

In this case, a picture that satisfies a predetermined condition will bereferred to as an advance picture. The predetermined condition for thepicture is: (1) the picture refers to a picture included in a randomaccess unit immediately before the random access unit including thepicture in question in the decoding order; and (2) the picture isbefore, in the display order, any of the pictures included in the randomaccess unit immediately before the random access unit including thepicture in question in the decoding order. It should be noted that therandom access unit is a unit defined by the encoding order and thedecoding order, and the encoding order and the decoding order are thesame. Further, a random access unit existing immediately before therandom access unit including the advance picture, such as the firstrandom access unit, will be referred to as an open end random accessunit. A picture which is included in the open end random access unit andwhich is after the advance picture in the display order will be referredto as an isolated picture. For example, In FIG. 4, picture B11 is anadvance picture, and picture P12 is an isolated picture.

FIG. 6 is a diagram illustrating another example of encoding a motionpicture by using three layers according to the present exemplaryembodiment.

Image encoding apparatus 10 according to the present exemplaryembodiment may encode an image so as not to generate any open end randomaccess unit as illustrated in FIG. 6 when temporal scalability isrealized by using three layers.

In the display order, any of the pictures included in the second randomaccess unit is after picture P12 which is the last of the first randomaccess unit. Therefore, all the pictures included in the second randomaccess unit do not become advance pictures. As a result, the firstrandom access unit does not become an open end random access unit.However, since picture B2 is after picture B1 in the decoding order,picture B1 cannot refer to picture B2. Likewise, since picture B6 isafter picture B5 in the decoding order, picture B5 cannot refer topicture B6. As described above, the prediction structure of the pictureseach with Temporal ID of 2 is restricted.

In the example of FIGS. 4 to 6, the cases where the number of layers isthree and four have been explained using examples of temporalscalability of 60 fps and 120 fps. However, a combination of framerates, and the number of layers that can be realized are not limited tothe above. This can be realized as long as the following condition isguaranteed: where a display interval of pictures for a frame rate ofdisplay is denoted as T_pts when only pictures of low layer are decodedand displayed, a decoding interval of given pictures which arecontinuous in the decoding order is the same as T_pts or equal to ormore than T_pts. Image encoding apparatus 10 dynamically encodes imagesin such a manner as to satisfy this condition.

FIG. 7 is a diagram for explaining image decoding apparatus 20 accordingto the present exemplary embodiment.

Image decoding apparatus 20 according to the present exemplaryembodiment obtains an encoded stream generated by image encodingapparatus 10 explained above. Image decoding apparatus 20 displays amotion picture at a frame rate of 120 fps by decoding all the picturesincluded in this encoded stream. Image decoding apparatus 20 displays amotion picture at a frame rate of 60 fps by decoding some of theplurality of pictures included in this encoded stream. For example, someof the plurality of pictures included in the encoded stream are aplurality of picture each of which belongs to one of layers other thanthe highest layer.

As described above, in the present exemplary embodiment, the decodingtimes of the plurality of pictures which do not belong to the highestlayer (hereinafter referred to as lower layer pictures) included in theencoded stream are spaced at regular intervals. Therefore, when theimage decoding apparatus decodes only the plurality of lower layerpictures in the encoded stream, the image decoding apparatus can decodethe lower layer pictures in order at every lapse of regular interval oftime. Therefore, by setting the regular interval to an appropriate time(for example, 2T= 1/60 seconds as described above), the processing loadof the image decoding apparatus can be alleviated. More specifically,the image decoding apparatus can perform decoding at a frame rateaccording to the processing performance of the image decoding apparatuswithout performing decoding of each picture at a high frame rate. Forexample, when an encoded stream of 60 fps is decoded, a time it takes todecode a single picture may be guaranteed to be equal to or less than1/60 seconds.

First Modification

In this case, a DTS of a leading picture of a random access unit will beexplained.

FIG. 8 is a diagram illustrating the decoding order and the displayorder of pictures and DTS and PTS (Presentation Time Stamp: displaytime) of pictures when the encoded stream as illustrated in FIG. 4 isreproduced at 120 fps.

In this case, a subscript (number) for each of DTS and PTS denotesdisplay order. For example, in MPEG-2 TS (Transport Stream) forbroadcasting, DTS or PTS is indicated by a header of a PES packet. InMMT (MPEG Media Transport) or RTP (Real-time Transport Protocol), DTS orPTS is indicated by, for example, a header of a packet in a transportlayer or header information of an encoded stream included in a payload.In a format of a type in which a file is transmitted without beingconverted into packets such as MPEG-DASH (Dynamic Adaptive Streamingover HTTP), DTS or PTS is included in a header portion of a file.Alternatively, in MPEG-4 AVC or HEVC, DTS or PTS can be indicated in anencoded stream by using SEI (Supplemental Enhancement Information) suchas Picture Timing SEI or Buffering Period SEI.

In a conventional encoded stream, when the interval of PTS in twopictures displayed at a fixed frame rate and continuous in the displayorder is denoted as T, the interval of DTS in two pictures continuous inthe decoding order is always T. Therefore, when the reproductionapparatus (or image decoding apparatus) starts decoding a leadingpicture in the decoding order at timing of DTS, the reproductionapparatus (or image decoding apparatus) may decode subsequent picturesin order at every interval of T without referring to DTS of subsequentpictures.

On the other hand, in the encoded stream according to the presentexemplary embodiment, as illustrated in FIG. 8, an interval of DTSbetween picture I0 and picture P4 and an interval of DTS between pictureP4 and picture B2 are 2T (T is, for example, 1/120 seconds). An intervalof DTS between picture B2 and picture B1 and an interval of DTS betweentwo pictures continuous after picture B1 in the decoding order are T.Therefore, in the encoded stream according to the present exemplaryembodiment, the interval of DTS between pictures is variable.Accordingly, the image decoding apparatus (or the reproductionapparatus) needs to refer to DTS for each picture, and decode thepicture at the timing of DTS.

Image decoding apparatus 20 according to the present modificationdecodes and displays pictures on the basis of timing of a videoprocessing signal generated at a regular interval. For example, when theframe rate of the display is 120 fps, image decoding apparatus 20generates a video processing signal at every T (for example, 1/120seconds), and decodes and displays a picture at the timing of generationof the video processing signal. In the encoded stream as illustrated inFIG. 8, an interval of DTS between picture I0 and picture P4 and aninterval of DTS between picture P4 and picture B2 are twice the cycle Tof the video processing signal. Further, an interval of DTS between twopictures continuous after picture B2 in the decoding order is the sameas the cycle T of the video processing signal.

FIG. 9 is a block diagram illustrating a configuration of image decodingapparatus 20 according to the present modification.

Image decoding apparatus 20 according to the present modification hasthe same function as image decoding apparatus 20 according to theexemplary embodiment, and decodes an encoded picture at timing indicatedby DTS of the picture. Image decoding apparatus 20 as described aboveincludes signal interval setter 21, DTS obtainer 22, determiner 23, anddecoder 24.

FIG. 10 is a flowchart illustrating an example of operation in whichimage decoding apparatus 20 according to the present modificationdecodes pictures in all layers.

First, signal interval setter 21 of image decoding apparatus 20 sets aninterval or a cycle for generating a video processing signal(hereinafter referred to as V_period) such that V_period becomes areciprocal of a frame rate for decoding and displaying all layers (stepS21).

Subsequently, DTS obtainer 22 obtains DTS of a picture to be decoded(hereinafter referred to as dts_i) from a header of a PES packet and thelike which stores encoded data of the picture (step S22). Subsequently,determining unit 23 monitors timing at which the video processing signalis generated, and determines whether the timing matches dts_i (stepS23). When the interval of DTS of the picture is N times as large asV_period, timing at which a video processing signal is generated in theN times counted from the decoding time of the picture that is decodedimmediately before matches dts_i. When the timing is determined to matchdts_i (“YES” in step S23), decoder 24 decodes the picture to be decoded(step S24). On the other hand, when the timing is determined not tomatch dts_i (“NO” in step S23), determining unit 23 repeatedly executesthe processing in step S23.

It should be noted that step S21 may be carried out once before thedecoding of the head picture is started, and it is not necessary toperform step S21 for every decoding of a picture. In the determinationin step S23, when a difference value between the timing at which thevideo processing signal is generated and dts_i is less than apredetermined threshold value, both may be determined to match eachother. The operation as illustrated in FIG. 10 can be applied to notonly the temporal scalability between the decoding of all the layers andthe decoding of low layers but also temporal scalability between twodifferent low layers.

As described above, in image decoding apparatus 20 according to thepresent modification, in a case where the interval of DTS can beexpressed as an integral multiple of a cycle of the video processingsignal even if the interval of DTS is variable, the picture can bedecoded in accordance with variable DTS. As a result, the amount ofprocessing for determining the timing of decoding can be reduced.

In this case, the following case will be considered: a frame rate whereall the layers are decoded (hereinafter referred to as FrameRateAll) isnot an integral multiple of a frame rate where only low layers aredecoded (hereinafter referred to as FrameRatePart) like temporalscalability of 50 fps and 120 fps. At this occasion, in order toguarantee decoding with the image decoding apparatus having a decodingperformance of 50 fps, the interval of DTS in a case of decoding onlylow layers needs to be 1/50 seconds. However, since FrameRateAll is notan integral multiple of FrameRatePart, the decoding intervals ofpictures during reproduction at 120 fps are not constant (that is, afixed interval), and in addition, the interval of DTS ( 1/50 seconds)does not become an integral multiple of the cycle of the videoprocessing signal ( 1/120 seconds). As a result, decoding cannot beperformed at a time indicated by DTS, and an overflow or an underflowmay occur in, for example, a buffer of an encoded picture. Therefore,when image encoding apparatus 10 according to the present modificationprovides temporal scalability, image encoding apparatus 10 according tothe present modification may determine a combination of layers forrealizing the temporal scalability such that the frame rate of displayin a case where all the layers are decoded becomes an integral multipleof a frame rate of display in a case where only low layers are decoded.Alternatively, image encoding apparatus 10 may store, in an encodedstream, information indicating that the frame rate in the case where allthe layers are decoded becomes an integral multiple of the frame rate ina case where only some of the layers are decoded. Still alternatively,image encoding apparatus 10 may store the information in a descriptor ina TS (TransportStream) constituted by multiplexing the encoded stream.

In a random access unit, a difference between DTS of the leading picturein the decoding order and PTS of the leading picture in the displayorder will be referred to as a display delay. In the example asillustrated in FIG. 8, a difference between DTSO and PTSO is a displaydelay. In a conventional encoded stream in which the frame rate of thedisplay is fixed, the interval of DTS is fixed and is the same as theinterval of PTS. Therefore, the display delay is expressed by a valueobtained by multiplying a number of pictures decoded until the PTS ofthe leading picture in the display order by the interval of PTS. In theexample as illustrated in FIG. 8, there are two pictures, that is,picture I0 and picture P4, which are decoded until the PTS of pictureI0, and accordingly, in a conventional calculation method, the displaydelay is calculated as 2×T. However, in the example as illustrated inFIG. 8, the interval of PTS between picture I0 and picture P4 and theinterval of PTS between picture P4 and picture B2 are twice that of T.Therefore, the actual display delay is 4×T. Thus, in a conventionalmethod, the display delay cannot be expressed appropriately.

Therefore, image encoding apparatus 10 according to the presentmodification may incorporate, into an encoded stream, informationindicating that how many times the display delay becomes as that of theinterval of PTS in order to correctly express the display delay even inan encoded stream in which the interval of DTS is not constant. In theexample as illustrated in FIG. 8, the interval of PTS is T, and thedisplay delay is four times of T, and therefore, image encodingapparatus 10 expresses the display delay as four. Alternatively, imageencoding apparatus 10 may indicate the display delay as an actual timelength such as “4×T”. In a case where a number of pictures decoded untilthe PTS of the leading picture in the display order is necessary, imageencoding apparatus 10 may indicate the number of pictures separatelyfrom the information indicating the display delay. Image encodingapparatus 10 may seamlessly connect a plurality of streams, or aplurality of particular sections of the stream, or the like. At thisoccasion, image encoding apparatus 10 encodes the streams or theparticular sections such that the display delays become equal byconsidering that the interval of DTS is variable in the streams or theparticular sections before and after the connection. At this occasion,image encoding apparatus 10 may store, in an encoded stream, informationindicating that the display delays are equal before and after theseamless connection. When image encoding apparatus 10 encodes streamsseamlessly connected with each other, image encoding apparatus 10 maynot encode the streams such that the number of pictures decoded untilthe PTS of the leading picture in the display order before the seamlessconnection is equal to the number of pictures decoded until the PTS ofthe leading picture in the display order after the seamless connection,and instead, image encoding apparatus 10 may encode streams such thatthe display delays defined by the present modification are the same.

In a case where the frame rate of the display is constant, that is, theinterval of PTS is constant, image encoding apparatus 10 according tothe present modification may signal auxiliary information indicatingthat the interval of DTS is not constant. For example, the auxiliaryinformation is a flag indicating whether the interval of DTS is constantor not. In this case, in a case where a flag indicating that theinterval of DTS is not constant is set, image decoding apparatus 20performs operation as illustrated in FIG. 10, and in a case where a flagindicating that the interval of DTS is not constant is not set, theinterval of DTS is constant, and therefore, image decoding apparatus 20may operate without referring to DTS for every picture.

Image encoding apparatus 10 according to the present modification mayset the auxiliary information may set the auxiliary information for eachrandom access unit, or may set the auxiliary information for eachencoded stream unit or a unit referred to by a play list in accumulatedcontent. The auxiliary information may be stored in any of an area forstoring private data in TS packet (such as private_data_bytes),management information about the contents of accumulated content, or aplurality of layers of a transmission and reception system of contentsuch as SEI of an encoded stream such as MPEG-4 AVC or HEVC. However,since it is preferable that the auxiliary information can be referred tobefore the encoded stream is decoded, image encoding apparatus 10 maystore the auxiliary information in a higher layer of a transmission andreception system of content such as a multiplex layer, such as TS ormanagement information about multiplexed data. As described above, inthe present modification, non-regular interval information indicatingthat the decoding times determined for the plurality of picturesincluded in a motion picture are not spaced at regular intervals isincluded, as the auxiliary information, in the encoded stream.

When image encoding apparatus 10 according to the present modificationdecodes only the low layers of an encoded stream having temporalscalability, image encoding apparatus 10 according to the presentmodification may store, in the encoded stream, information indicatingthat the interval of DTS of any given two pictures continuous in thedecoding order is variable. When the frame rate of the display in thecase where only the low layers are decoded (hereinafter referred to asframe_rate) is considered to be constant, this information indicatesthat the interval of DTS of any given two pictures continuous in thedecoding order is the same as 1/frame_rate (seconds) or equal to or morethan 1/frame_rate (seconds). For example, in MPEG2-TS, identificationinformation about an encoded stream constituting a program is shown inPMT (Program Map Tables). Image encoding apparatus 10 according to thepresent modification may show the information by defining a descriptorin PMT. For example, in a case where a descriptor in PMT indicates thatthe interval of DTS is less than 1/60 seconds, image decoding apparatus20 having a decoding performance up to 60 fps does not perform decodingor reproduction of the encoded stream. Alternatively, image decodingapparatus 20 may perform operation of setting DTS again such that thedecoding interval of each picture is equal to or more than 1/60 seconds,and decoding each picture. In a case where the operation of setting DTSagain involves changing PTS, image decoding apparatus 20 also changesPTS.

Second Modification

Subsequently, a change of a decoding time of a picture will beexplained.

When image decoding apparatus 20 according to the exemplary embodimentdecodes all the layers, image decoding apparatus 20 may change DTS of apicture before the start of decoding such that the interval of DTSbecomes 1/frame_rate (seconds).

FIG. 11 is a diagram illustrating an example of changing DTS.

As illustrated in FIG. 11, image decoding apparatus 20 according to thepresent modification changes the DTSs of picture I0 and picture P4 sothat all the intervals of DTSs are set to 1/frame_rate (seconds). Apicture of which interval of DTS is variable is a picture that isdecoded before the PTS of the leading picture in the display order. Bychanging the DTSs of these pictures, the interval of DTS can beguaranteed to be fixed. When the interval of DTS is fixed, the timing ofdecoding of a picture can be determined and decoding can be performedaccording to the same method as the conventional method. It should benoted that only the DTS of a picture that is decoded before the PTS ofthe leading picture in the display order is changed to be delayed, andthe changed interval of DTS is 1/frame_rate (seconds). Therefore, anyparticular problem would not occur in a decoder model such as HRD(Hypothetical Reference Decoder) in MPEG-4 AVC or HEVC.

When image encoding apparatus 10 according to the present modificationmultiplexes encoded streams with TS, image encoding apparatus 10according to the present modification may indicate a changed value ofDTS in TREF (Timestamp Reference) field and the like in PES header. In acase where another multiplex method is used, image encoding apparatus 10may also indicate DTSs before the change and after the change. Further,information indicating a corresponding relationship between a layer tobe decoded and used DTS or PTS, for example, an indication of use ofchanged DTS in a case where all the layers are decoded, may be indicatedin, for example, a descriptor in a TS, program information in atransport layer, or management information in accumulated content. Imageencoding apparatus 10 may indicate information indicating that thechanged interval of DTS is fixed or the interval is equal to theinterval of PTS, in program information in a transport layer ormanagement information in accumulated content.

By doing so, even if the processing performance is low, image decodingapparatus 20 can decode only the low layer. Image decoding apparatus 20having high processing performance for decoding all the layers analyzesa descriptor of MPEG-2 TS and the like or determines whether thereexists a TREF field of a PES packet header, so that Image decodingapparatus 20 can find that the changed DTS or PTS is transmitted.Therefore, image decoding apparatus 20 can decode the encoded stream byusing the changed DTS or PTS.

In a case where image decoding apparatus 20 records an encoded streambased on the assumption that all the layers can be decoded, the encodedstream in which the DTS has been changed as described above may berecorded. At this occasion, instead of using a filed for storing achanged DTS or PTS such as TREF, a field of DTS or PTS of the PES headermay be changed.

Third Modification

Subsequently, auxiliary information for playback control will beexplained.

FIG. 12 is a diagram for explaining pictures decoded in an open endrandom access unit.

For example, in the example as illustrated in FIG. 12, an end of anaccumulated encoded stream or an encoded stream obtained via acommunication network matches an end of a first random access unit whichis an open end random access unit. At this occasion, pictures B11, B13,B14, B15 included in a second random access unit cannot be decoded.However, picture P12 which belongs to the first random access unit canbe decoded. In this case, picture B11 is an advance picture, and pictureP12 is an isolated picture.

It should be noted that in a random access unit in an encoded stream,all the pictures constituting the random access unit except apredetermined picture can be decoded without referring to other randomaccess units. In a case where a random access unit is configured as anopen GOP (Group Of Pictures), a predetermined picture is a picture thatis before, in the display order, the leading picture in the decodingorder, in the random access unit. Such a predetermined picture may referto a picture included in the random access unit immediately before therandom access unit of the predetermined picture in the decoding order.Therefore, in a case where decoding is started from the head of therandom access unit which is an open GOP, the predetermined picturecannot be decoded. Therefore, the image decoding apparatus decodes anddisplays, as a picture that can be decoded, each of all the pictures inthe random access unit that are after, in display order, the leadingpicture in the decoding order.

In this case, image decoding apparatus 20 that has obtained encoded dataup to the open end random access unit in the encoded stream has notobtained an advance picture, and therefore, image decoding apparatus 20cannot decode the advance picture. For this reason, image encodingapparatus 10 according to the present modification incorporated, intothe encoded stream, auxiliary information for reproduction control.

The auxiliary information for reproduction control is, for example,information as shown in (1) to (5) below: (1) information indicatingwhether or not the random access unit is an open end random access unit;(2) information indicating whether or not the random access unit is alast random access unit in a section continuously placed back, such asthe end of the encoded stream or the last random access unit indicatedby a play list and the like; (3) information indicating whether or notthe picture is an isolated picture, or information indicating whether ornot the picture is a last isolated picture in the display order in therandom access unit; (4) information indicating whether or not thepicture is an advance picture; and (5) information indicating whether ornot there is an isolated picture that is after, in display order, adesignated picture in the random access unit. It should be noted that,in the (2), in a case where discontinuous sections in an encoded stream,encoded streams different from each other, and the like are coupled, arandom access unit before the coupled portion cannot refer to a picturein a subsequent random access unit. Therefore, the random access unitbefore the coupled portion is also treated in the same manner as thelast random access unit in the reproduction section.

Image encoding apparatus 10 according to the present modification mayset the auxiliary information for reproduction control for each randomaccess unit, for each encoded stream unit, or for each unit referred toby a play list in accumulated content. The auxiliary information can bestored in any of an area for storing private data in TS packet (such asprivate_data_bytes), management information about the contents ofaccumulated content, or a plurality of layers of a transmission andreception system of content such as SEI of an encoded stream such asMPEG-4 AVC or HEVC. However, since it is preferable that the auxiliaryinformation can be referred to before the encoded stream is decoded,image encoding apparatus 10 may store the auxiliary information in ahigher layer of a transmission and reception system of content such as amultiplex layer such as TS or management information about multiplexeddata.

The above (1) and (2) information is attribute information indicating anattribute of a random access unit. Image encoding apparatus 10 storesthe attribute information in, for example, an SEI that is before, indecoding order, the head picture of the random access unit, or a packetheader or a payload in a transport layer such as a TS packet or an MMTpacket for storing the head picture of the random access unit, or atable for managing an attribute of a random access unit in managementinformation about content. In a case where, in a transport layer, forexample, information for indicating a random access point is signaledsuch as random_access_indicator of a TS packet, the attributeinformation may be stored in the packet indicating the random accesspoint.

The above (3) and (4) information is attribute information about eachpicture constituting the random access unit. Image encoding apparatus 10may collectively store the attribute information in the random accessunit, or may store the attribute information for each picture. In a casewhere the attribute information is stored for each picture, imageencoding apparatus 10 attaches an SEI to each random access unit in anencoded stream, or stores the attribute information in a header or apayload of a TS packet storing head data of a picture. Image encodingapparatus 10 may store attribute information about a picture only in acase where the random access unit is an open end random access unit.

Subsequently, an image decoding method of an open end random access unitwill be explained.

FIG. 13 is a flowchart illustrating an example of operation in whichimage decoding apparatus 20 according to the present modificationdecodes a motion picture on the basis of auxiliary information forreproduction control.

First, image decoding apparatus 20 determines whether or not thereexists auxiliary information for reproduction control in managementinformation about content, a transport layer such as a TS, or an encodedstream (step S211). In a reproduction section reproduced continuously,auxiliary information for reproduction control is either provided or notprovided in all the random access units constituting the reproductionsection. Therefore, the processing of step S211 is performed only on therandom access unit at the head in the reproduction section.

In this case, in a case where it is determined that there existsauxiliary information for reproduction control (“YES” in step S211),image decoding apparatus 20 performs the processing of step S212, and ina case where it is determined that there does not exist auxiliaryinformation for reproduction control (“NO” in step S211), image decodingapparatus 20 performs the processing of step S215.

In step S215, image decoding apparatus 20 determines a picture to bedecoded, on the basis of a method defined in advance (step S215). Instep S212, image decoding apparatus 20 determines whether or not thefollowing condition is satisfied: the random access unit to be decodedis the last random access unit in the section reproduced continuously,and is an open end random access unit (step S212).

In this case, in a case where the condition is determined to besatisfied (“YES” in step S212), image decoding apparatus 20 determines apicture to be decoded, by referring to the auxiliary information forreproduction control (step S213). On the other hand, in a case where thecondition is determined not to be satisfied (“NO” in step S212), imagedecoding apparatus 20 determines to decode all the pictures included inthe random access unit (step S214). However, at this occasion, in a casewhere the random access unit to be decoded is a random access unit atthe head in the reproduction section, image decoding apparatus 20 doesnot decode a picture that refers to a picture included in a randomaccess unit immediately before the random access unit to be decoded inthe decoding order.

Then, image decoding apparatus 20 decodes a picture determined inprocessing in any one of steps S213, S214, and S215 (step S216).

It should be noted that the processing of step S212 may be performed foreach random access unit. In a case where the auxiliary information ofeach of the plurality of pictures is collectively stored in the randomaccess unit, the determination of the picture in step S213 is performedat the start of decoding of the random access unit. In a case where theauxiliary information of each of the plurality of pictures is stored foreach picture, the determination of the picture is performed for eachpicture.

It should be noted that in a case where the auxiliary information forreproduction control does not indicate the information of the picturefor each picture, image decoding apparatus 20 may determine whether ornot there exists a picture referred to in step S213. Accordingly, imagedecoding apparatus 20 determines whether or not a picture can be decodedand can determine the picture to be decoded.

It should be noted that image decoding apparatus 20 may perform thedetermination of the picture in step S213 as follows.

For example, image decoding apparatus 20 determines only a picture thatis before the advance picture in display order to be a picture to bedecoded, and determines an isolated picture to be a picture that is notdecoded.

Alternatively, image decoding apparatus 20 determines a picture that isbefore the advance picture in display order and an isolated picture tobe pictures that are to be decoded. An advance picture that is beforethe isolated picture in display order cannot be decoded. Therefore, attiming indicated by the PTS of the advance picture, image decodingapparatus 20 freezes and displays a decoded result of a picture that canbe decoded and that is immediately before the advance picture in thedisplay order. More specifically, image decoding apparatus 20 alsocontinuously displays a decoded result of a picture immediately beforethe advance picture at the timing indicated by the PTS of the advancepicture. Alternatively, image decoding apparatus 20 may display adecoded result of a picture that can be decoded and that is immediatelybefore the advance picture in the display order and an image obtained byinterpolating the decoded result of the advance picture.

In this case, image decoding apparatus having decoding performance of120 fps decodes only pictures which belong to a layer with Temporal IDof 0 at a decoding interval of 120 fps, thus performing specialreproduction such as performing reproduction with four times speed.Therefore, a method for determining a picture to be decoded may beswitched between a normal reproduction, in which pictures in all thelayers are decoded and displayed, and a special reproduction. Forexample, in the example as illustrated in FIG. 1A or FIG. 1B, thepictures each with Temporal ID of 0 are only an I picture and a Ppicture, and the advance picture is not included in these pictures.Therefore, image decoding apparatus 20 may not decode the isolatedpicture during the normal reproduction, and in a case where only thepictures which belong to the layer with Temporal ID of 0 are decoded andreproduced during the special reproduction, image decoding apparatus 20may decode the isolated picture. More generally, in a case of specialreproduction, image decoding apparatus 20 may decode only a picturewhich is in a layer to be decoded and which is before the advancepicture in display order.

In a case where the random access unit is an open end random accessunit, image encoding apparatus 10 may store, in an encoded stream,information for identifying the advance picture or a last isolatedpicture in the display order as the attribute information of the randomaccess unit. For example, when the decoding order of the advance pictureis considered to be the N-th in the random access unit, image decodingapparatus 20 determines to decode only a picture having a PTS before thePTS of the N-th picture. Alternatively, when the last isolated picturein the display order is the N-th in the decoding order, image decodingapparatus 20 determines to decode a picture that is after the isolatedpicture in display order.

Fourth Modification

For example, in a case where image decoding apparatus 20 according tothe present modification in which 60 fps is the upper limit of thedecoding performance obtains an encoded stream at frame rate more than60 fps, image decoding apparatus 20 according to the presentmodification may convert DTS or PTS of each picture included in theencoded stream such that the picture can be decoded. For example, in acase where image decoding apparatus 20 obtains and records an encodedstream via a broadcast or communication network, image decodingapparatus 20 may convert DTS or PTS. Alternatively, when image decodingapparatus 20 transmits an encoded stream recorded on a memory, a harddisk, and the like to an external device by using a communicationnetwork or the like, image decoding apparatus 20 may convert DTS or PTS.

FIG. 14 is a diagram illustrating an example of a conversion of DTS orPTS. A first line from the top in FIG. 14 indicates original DTSs of allthe pictures constituting all the layers included in an original encodedstream. When all the pictures are decoded and displayed, a motionpicture is displayed at a frame rate of 120 fps. A second line from thetop in FIG. 14 indicates each of recorded pictures and original DTSs ofthese pictures when the original encoded stream is recorded as anencoded stream of 60 fps. In an encoded stream of 60 fps recorded inthis manner, the interval of DTS between pictures is not guaranteed tobe 1/60 (seconds).

A third line from the top in FIG. 14 indicates each of recorded picturesand changed DTSs of these pictures when the original encoded stream isrecorded as an encoded stream of 60 fps. Image decoding apparatus 20according to the present modification performs changes of DTSs asindicated in this third line. As a result of the changes of the DTSs,the interval of DTS between pictures is guaranteed to be 1/60 (seconds).A fourth line from the top in FIG. 14 indicates each of recordedpictures and original PTSs of these pictures when the original encodedstream is recorded as an encoded stream of 60 fps. It is not necessaryto change the PTS, and the same value as the original PTS can be used.In this case, the DTS is changed to be delayed from the original DTS,and the PTS is not changed. Therefore, neither overflow nor underflowoccurs in a buffer in a previous stage provided in image decodingapparatus 20 (corresponding to Coded Picture Buffer of MPEG-4 AVC orHEVC), or a buffer for holding a reference picture (corresponding toDecoded Picture Buffer of MPEG-4 AVC or HEVC).

It should be noted that in a case where it is necessary to change PTS,the PTS may be changed so as to satisfy the buffer model (correspondingto Hypothetical Reference Decoder of MPEG-4 AVC or HEVC). When theencoded stream is multiplexed by MPEG-2 TS, the PTS or DTS is indicatedin a header of a PES packet. Therefore, image decoding apparatus 20 maychange the PTS or DTS in the header of the PES packet. Alternatively,image decoding apparatus 20 may not change the value of the PTS or DTS,and may store the changed value in a TREF (Timestamp Reference) field ofa PES packet header. Alternatively, image decoding apparatus 20 maychange the PTS or DTS, and then, image decoding apparatus 20 may storethe value of the original PTS or DTS in a TREF field.

In the exemplary embodiment and the modification thereof, thedescription has been given of, as an example, temporal scalable based ona combination of 60 fps and 120 fps, but the present disclosure may beapplied to temporal scalable of a combination of other frame rates. Inthe exemplary embodiment and the modification thereof, as a layerdecoded so as to realize temporal scalable, a combination of all thelayers and layers other than the highest layer has been explained as anexample, but the exemplary embodiment and the modification thereof canalso be applied to layers of other combinations.

Hereinabove, the image encoding apparatuses and the image decodingapparatuses according to one or a plurality of aspects have beenexplained on the basis of the exemplary embodiment and the modificationthereof, but the present disclosure is not limited to this exemplaryembodiment and the modification thereof.

FIG. 15A is a block diagram illustrating an image encoding apparatusaccording to an aspect of the present disclosure.

Image encoding apparatus 100 according to an aspect of the presentdisclosure is an apparatus for encoding a motion picture for eachpicture which belongs to any one of a plurality of layers, withoutreferring to another picture which belongs to a layer higher than thelayer to which the picture in question belongs, and includes decidingunit 101, encoder 102, and generator 103.

Deciding unit 101 determines decoding times of a plurality of picturesincluded in the motion picture such that decoding times of a pluralityof lower layer pictures which are some pictures of the plurality ofpictures included in the motion picture and which do not belong to ahighest layer of the plurality of layers are not spaced at regularintervals. At this occasion, further, deciding unit 101 determinesdecoding times of a plurality of pictures included in the motion picturesuch that timing for decoding each of the plurality of lower layerpictures is caused to be the same between a case where the plurality ofencoded pictures included in the motion picture are decoded and a casewhere only the plurality of lower layer pictures of the plurality ofpictures are decoded

Encoder 102 encodes each of the plurality of pictures included in themotion picture in accordance with encoding order according to thedecoding times thus determined. Generator 103 generates an encodedstream including the plurality of encoded pictures and decoding timesthat are determined for the plurality of pictures.

FIG. 15B is a flowchart illustrating an image encoding method accordingto one aspect of the present disclosure.

The image encoding method according to one aspect of the presentdisclosure is a method in which image encoding apparatus 100 encodes amotion picture for each picture which belongs to any one of a pluralityof layers, without referring to another picture which belongs to a layerhigher than the layer to which the picture in question belongs. Thisimage encoding method includes step S101, step S102, and step S103. Instep S101, decoding times of a plurality of pictures included in themotion picture are determined such that decoding times of a plurality oflower layer pictures which are some pictures of the plurality ofpictures included in the motion picture and which do not belong to ahighest layer of the plurality of layers are spaced at regularintervals. At this occasion, further, decoding times of a plurality ofpictures included in the motion picture are determined such that timingfor decoding each of the plurality of lower layer pictures is caused tobe the same between a case where the plurality of encoded picturesincluded in the motion picture are decoded and a case where only theplurality of lower layer pictures of the plurality of pictures aredecoded

In step S102, each of the plurality of pictures included in the motionpicture is encoded in accordance with encoding order according to thedecoding times thus determined. In step S103, an encoded stream isgenerated that includes the plurality of encoded pictures and decodingtimes that are determined for the plurality of pictures

Therefore, each of the plurality of pictures included in the encodedstream is encoded without referring to another picture which belongs toa layer higher than the layer to which the picture in question belongs.Therefore, the image decoding apparatus can decode only the plurality oflower layer pictures in the encoded stream. The decoding times of theplurality of lower layer pictures included in the encoded stream arespaced at the regular intervals. Therefore, when the image decodingapparatus decodes only the plurality of lower layer pictures in theencoded stream, the image decoding apparatus can decode these lowerlayer pictures in order at every lapse of regular interval of time.Therefore, by setting the regular interval to an appropriate time suchas 1/60 seconds, the processing load of the image decoding apparatus canbe alleviated. More specifically, the image decoding apparatus canperform decoding at a frame rate such as 60 fps according to theprocessing performance of the image decoding apparatus withoutperforming decoding of each picture at a high frame rate such as 120fps. Further, timing for decoding each of the plurality of lower layerpictures is the same between the case where the plurality of picturesincluded in the encoded stream (for example, all the pictures) aredecoded and the case where only the plurality of lower layer pictures ofthe plurality of pictures are decoded. For example, as illustrated inFIG. 4 or FIG. 6, pictures I0, P4, B2, I8, B6, and the like which arethe plurality of lower layer pictures are decoded at the same timingbetween the case where the decoding is performed at 120 fps and the casewhere the decoding is performed at 60 fps. Therefore, the image decodingapparatus does not need to change the timing for decoding each of theplurality of lower layer pictures between the case where all thepictures of the encoded stream are decoded and the case where only theplurality of lower layer pictures are decoded. Therefore, the processingload of the image decoding apparatus can be further alleviated.

In the determining of the decoding time in step S101, the decoding timeof each of the plurality of uppermost layer pictures which are somepictures of the plurality of pictures included in the motion picture andwhich belong to the highest layer is determined to be between thedecoding times of the plurality of lower layer pictures. For example, inthe example as illustrated in FIG. 6, the decoding time of picture B1which is an uppermost layer picture is determined to be between pictureP4 and picture B2 which are lower layer pictures, and the decoding timeof picture B3 which is an uppermost layer picture is determined to bebetween picture B2 and picture I8 which are lower layer pictures.

Therefore, when the encoded stream is decoded, the uppermost layerpicture and the lower layer picture are alternately decoded. Therefore,the interval of the time for decoding each of the plurality of lowerlayer pictures in the encoded stream is longer than the interval of thetime for decoding each of all the pictures of the decoded stream. As aresult, the image decoding apparatus can decode each picture at a surelylower frame rate when the image decoding apparatus decodes only theplurality of lower layer pictures than when the image decoding apparatusdecodes each of all the pictures in the decoded stream. Therefore, theprocessing load of the image decoding apparatus can be reliablyalleviated.

In the determining of the decoding time in step S101, the decoding timesof the plurality of pictures included in the motion picture aredetermined such that twice the time of the interval of decoding times ofan uppermost layer picture and a lower layer picture which are of theplurality of uppermost layer pictures and the plurality of lower layerpictures and which are continuous in the decoding order is equal to theregular interval of time explained above. For example, in the example asillustrated in FIG. 6, the interval of the decoding time of each ofpicture B1, that is, an uppermost layer picture, and picture B2, thatis, a lower layer picture, which are continuous in the decoding order isT= 1/120 seconds. Accordingly, in step S101, the decoding time of eachof the plurality of pictures included in the motion picture isdetermined such that 2×T= 1/60 seconds is equal to the regular intervalof time explained above.

Therefore, any interval of the decoding time of each of the plurality oflower layer pictures is the interval of the decoding time of each of anuppermost layer picture and a lower layer picture which are continuousin the decoding order, and more specifically, any interval of thedecoding time of each of the plurality of lower layer pictures is twicethe interval of the time for decoding each of all the pictures in thedecoded stream. Therefore, in a case where a frame rate for decoding anddisplaying all the pictures of the encoded stream is 120 fps, the imagedecoding apparatus can decode each of the plurality of lower layerpictures included in the encoded stream at a time interval of areciprocal of a frame rate of 60 fps without any load.

In a case where the motion picture includes a plurality of random accessunits including a plurality of pictures which are continuous in thedecoding order, the decoding time may be determined as follows in stepS101. More specifically, in step S101, the decoding time of each picturein the random access unit is determined for each of the random accessunits, such that, in the random access unit, all the pictures except apicture displayed, in display order, before a picture at a head indecoding order can be decoded without referring to a picture included inanother random access unit. In this case, the leading picture is an Ipicture (so-called IDR picture: Instantaneous Decoding Refresh Picture)in which a picture that is after the leading picture in decoding orderis prohibited from referring to a picture that is before the leadingpicture in decoding order. Alternatively, the leading picture is an Ipicture (so-called CRA picture: Clean Random Access Picture) in which apicture that is after the leading picture in decoding order and beforethe leading picture in display order is permitted to refer to a picturethat is before the leading picture in decoding order. For example, inthis step S101, image encoding apparatus 100 determines the decodingtime of each of the plurality of pictures included in the motion pictureas illustrated in FIG. 6. In this example as illustrated in FIG. 6,picture I16 is a CRA picture in which picture B13 that is before pictureI16 in display order refers to picture P12 in the first random accessunit.

Therefore, for each of the random access units, the image decodingapparatus can appropriately decode each of the plurality of picturesincluded in the random access unit.

Description will now be given in detail of processing operation in whichimage encoding apparatus 100 determines decoding times of the pluralityof pictures included in the motion picture as shown in the example ofFIG. 6 in step S101.

In a case where a frame rate at which all the pictures included inencoded motion pictures are decoded and displayed is, for example, 120fps, image encoding apparatus 100 determines the decoding time of eachof all the pictures with a time unit ( 1/120 seconds) of the reciprocalof the frame rate (120 fps) in step S101. More specifically, thedecoding time determined for each picture is expressed by a timeobtained by adding an offset value to an integral multiple of the timeunit. In step S101, first, image encoding apparatus 100 may determineTId of each of the plurality of pictures included in the motion picture,and may thereafter determine decoding order of each of the plurality ofpictures. Then, image encoding apparatus 100 determines the DTS of eachof the plurality of pictures with the time unit on the basis of thedecoding orders thus determined.

For example, for each picture disposed in the display order, imageencoding apparatus 100 determines TId which is a value for identifyingthe layer of the picture in a range equal to or more than zero and equalto or less than K (K is an integer equal to or more than 1). A layerwith TId of K is the highest layer, and a layer with TId of 0 is thelowest layer. More specifically, deciding unit 101 determines TId of theleading I picture of the plurality of pictures arranged in the displayorder in the motion picture to be 0. Further, for every M (M is aninteger equal to or more than 2) pictures (hereinafter referred to as apicture set) which are continuous in the plurality of picture subsequentto the leading I picture arranged in the display order, deciding unit101 determines TId of the I picture or P picture which is the lastpicture of the picture set to be zero. In the picture set, the lastpicture in the display order is the I picture or P picture, TId of the Ipicture or P picture is determined to be 0. A picture of which TId isdetermined to be 0 is hereinafter referred to as the 0th hierarchicalpicture. For example, in the example as illustrated in FIG. 1A, fourpictures including picture B1, picture B2, picture B3, and picture P4correspond to the picture set. Then, picture P4 is determined to be the0th hierarchical picture.

Subsequently, deciding unit 101 identifies, as a candidate picture, atleast one picture which is other than the 0th hierarchical pictureincluded in the picture set (for example, B picture) and which is acandidate for which TId is determined. This candidate picture is apicture that is displayed between two already-determined pictures ofwhich TId are already determined. For example, in the example asillustrated in FIG. 1A, in a case where TId of each of picture I0 andpicture P4 is already determined, picture I0 and picture P4 arealready-determined pictures. In this case, in the picture set includingpictures B1 to B3 and picture P4, picture B2 which is a picturedisplayed between picture I0 and picture P4 is identified as thecandidate picture.

Further, when there are a plurality of candidate pictures thusdetermined, deciding unit 101 determines TId of the candidate leadingpicture in the display order among the plurality of candidate picturesto be a value N obtained by adding one to TId which is one of TIds ofthe two already-determined pictures, whichever is not a smaller one,corresponding to the candidate leading picture. For example, in theexample as illustrated in FIG. 1B, in a case where TId of each ofpicture I0, picture P8, and picture B4 is already determined, pictureI0, picture P8, and picture B4 are already-determined pictures. In thiscase, in the picture set including pictures B1 to B7, and picture P8,picture B2 which is a picture displayed between picture I0 and pictureB4 and picture B6 which is a picture displayed between picture B4 andpicture P8 are identified as the candidate pictures. Therefore, decidingunit 101 determines TId of one of candidate pictures B2 and B6 that isat the head in the display order, that is, TId of candidate picture B2,to be a value (N=2) that is obtained by adding one to TId=1 of TId oftwo already-determined pictures I0 and B4, whichever is not a smallerone, corresponding to candidate picture B2 at the head.

Deciding unit 101 repeats identification of such candidate picture anddetermination of TId until N falls within a range equal to or less thanK and TIds of all the pictures other than the 0th hierarchical pictureincluded in the picture set are determined. As a result, as illustratedin FIG. 1A or FIG. 1B, TId is determined for each picture.

Subsequently, deciding unit 101 determines the leading I picture to be afirst element in the decoding order. For example, as illustrated in FIG.6, deciding unit 101 determines picture I0 which is the leading Ipicture to be a first element in the decoding order.

Then, for each of the picture sets explained above, deciding unit 101determines the decoding order of each of the plurality of pictures inthe picture set. More specifically, in that picture set, deciding unit101 determines the decoding order of the 0th hierarchical picture to bethe head. Then, deciding unit 101 makes determination in order from apicture that is before another picture in the display order among theplurality of pictures other than the 0th hierarchical picture includedin the picture set, and determines the decoding order of the picture inquestion to be immediately after the decoding order that has alreadybeen determined. For example, in the picture set including pictures B1to B7 and picture P8, deciding unit 101 determines the decoding order ofpicture P8 which is the 0th hierarchical picture to be at the head.Then, deciding unit 101 determines the decoding order of pictures B1 toB3 in such a manner that picture B1, picture B2, and picture B3 aresubsequent to picture P8.

Deciding unit 101 determines that the plurality of picture sets arrangedin the display order are decoded in arrangement order. Morespecifically, deciding unit 101 determines the decoding order at thehead in the picture set to be the last in the decoding order of apicture set immediately before in the display order, or to be an ordinalnumber obtained by adding one to the decoding order of the leading Ipicture explained above (picture I0).

Further, when deciding unit 101 determines the decoding time of theleading I picture (picture I0), deciding unit 101 determines thedecoding time of a picture (picture P4) immediately after the picture inquestion in the decoding order of the I picture to be a time obtained byadding the time unit ( 1/120 seconds)×2 explained above to the decodingtime of the I picture. Deciding unit 101 determines the decoding time ofeach picture that is after, in the decoding order, the picture (pictureP4) immediately after the picture in question, to be a time obtained byadding the time unit explained above to the decoding time of the pictureimmediately before the picture in question in the decoding order.

As described above, deciding unit 101 determines the decoding time ofeach picture, so that the decoding time of each of the plurality oflower layer pictures becomes an regular interval, that is, an intervalof the time unit ( 1/120 seconds)×2.

In the determining of the decoding time in step S101, in a case where aframe rate at which all the pictures included in the encoded motionpicture are decoded and displayed is f, the decoding time of each of allthe pictures is determined such that the decoding time of each of theplurality of lower layer pictures included in all the pictures is spacedapart by a time indicated by n times (n is an integer equal to or morethan 2) a reciprocal of the f.

Therefore, the image decoding apparatus can decode each of the pluralityof lower layer pictures at a time interval which is n times a reciprocalof that frame rate in order without any load.

In an image encoding method according to one aspect of the presentdisclosure, further, display delay information indicating a displaydelay which is a time between a decoding time of a picture at a head inthe decoding order included in the motion picture and a display time ofthe leading picture in the display order included in the motion picturemay be incorporated into the encoded stream.

Therefore, the image decoding apparatus can obtain the display delayinformation from the encoded stream. Therefore, as illustrated in FIG.8, when the image decoding apparatus starts decoding the encoded streamfrom a time before the display start time by the display delay indicatedby the display delay information, the image decoding apparatus candisplay the motion picture without delay from the display start time.

In an image encoding method according to one aspect of the presentdisclosure, further, non-regular interval information indicating thatdecoding times determined for the plurality of pictures included in themotion picture are not spaced at regular intervals may be incorporatedinto the encoded stream.

Therefore, the image decoding apparatus can obtain the non-regularinterval information from the encoded stream. Therefore, the imagedecoding apparatus can determine that each of the plurality of picturesincluded in the encoded stream cannot be decoded in order at the framerate of the display. As a result, in accordance with a flowchart asillustrated in FIG. 10, while the image decoding apparatus refers to thedecoding time determined for each of the plurality of pictures includedin the encoded stream, the image decoding apparatus can decode theplurality of pictures at appropriate timing.

FIG. 15C is a block diagram of an image decoding apparatus according toan aspect of the present disclosure.

Image decoding apparatus 200 according to an aspect of the presentdisclosure is an apparatus for decoding an encoded stream including anencoded motion picture for each picture which belongs to any one of aplurality of layers, without referring to another picture which belongsto a layer higher than the layer which the picture in question belongs.Image decoding apparatus 200 includes obtainer 201 and decoder 202.

Obtainer 201 obtains a decoding time of each of the plurality ofpictures included in the encoded stream from the encoded stream. In thiscase, the decoding time of each of the plurality of pictures isdetermined as follows. More specifically, these decoding times aredetermined such that decoding times of a plurality of lower layerpictures which are some pictures of the plurality of pictures includedin the encoded stream and which do not belong to a highest layer of theplurality of layers are spaced at regular intervals. Further, thesedecoding times are determined such that timing for decoding each of theplurality of lower layer pictures is caused to be identical between acase where the plurality of pictures included in the encoded stream aredecoded and a case where only the plurality of lower layer pictures ofthe plurality of pictures are decoded

Decoder 202 decodes each of the plurality of pictures included in theencoded stream or the plurality of lower layer pictures in accordancewith the obtained decoding time.

FIG. 15D is a flowchart illustrating an image decoding method accordingto an aspect of the present disclosure.

The image decoding method according to an aspect of the presentdisclosure is a method in which image decoding apparatus 200 decodes anencoded stream including an encoded motion picture for each picturewhich belongs to any one of a plurality of layers, without referring toanother picture which belongs to a layer higher than the layer which thepicture in question belongs. This image decoding method includes stepS201 and step S202.

In step S201, the decoding time of each of the plurality of picturesincluded in the encoded stream is obtained from the encoded stream. Inthis case, the decoding time of each of the plurality of pictures isdetermined as follows. More specifically, the decoding times aredetermined such that decoding times of a plurality of lower layerpictures which are some pictures of the plurality of pictures includedin the encoded stream and which do not belong to a highest layer of theplurality of layers are spaced at regular intervals. Further, thedecoding times are determined such that timing for decoding each of theplurality of lower layer pictures is caused to be identical between acase where the plurality of pictures included in the encoded stream aredecoded and a case where only the plurality of lower layer pictures ofthe plurality of pictures are decoded

In step S202, each of the plurality of pictures included in the encodedstream or the plurality of lower layer pictures is decoded in accordancewith the obtained decoding time.

Accordingly, each of the plurality of pictures included in the encodedstream is encoded without referring to another picture which belongs toa layer higher than the layer which the picture in question belongs.Therefore, image decoding apparatus 200 can decode only the plurality oflower layer pictures in the encoded stream. The decoding times of theplurality of lower layer pictures included in the encoded stream arespaced at the regular intervals. Therefore, when image decodingapparatus 200 decodes only the plurality of lower layer pictures in theencoded stream, image decoding apparatus 200 can decode the lower layerpictures in order at every lapse of regular interval of time. Therefore,when the regular interval is an appropriate time, the processing load ofimage decoding apparatus 200 can be alleviated. More specifically, imagedecoding apparatus 200 can perform decoding at a frame rate according tothe processing performance of image decoding apparatus 200 withoutperforming decoding of each picture at a high frame rate. Further,timing for decoding each of the plurality of lower layer pictures isidentical between the case where the plurality of pictures included inthe encoded stream (for example, all the pictures) are decoded and thecase where only the plurality of lower layer pictures of the pluralityof pictures are decoded. Therefore, image decoding apparatus 200 doesnot need to change the timing for decoding each of the plurality oflower layer pictures between the case where all the pictures of theencoded stream are decoded and the case where only the plurality oflower layer pictures are decoded. Therefore, the processing load ofimage decoding apparatus 200 can be further alleviated.

In an image decoding method according to an aspect of the presentdisclosure, further, in a case where decoding times of the plurality ofpictures included in the encoded stream are not spaced at the regularinterval, the decoding time of each of the plurality of pictures ischanged to have the regular interval, and in the decoding of the encodedstream, each of the plurality of pictures included in the encoded streamor the plurality of lower layer pictures may be decoded in accordancewith the changed decoding time.

Accordingly, for example, as illustrated in FIG. 11, the decoding timeof each of the plurality of pictures is changed to have the regularinterval, and therefore, image decoding apparatus 200 can decode each ofthe plurality of pictures included in the encoded stream at every lapseof regular interval of time. Therefore, the processing load of imagedecoding apparatus 200 can be further alleviated.

In an image decoding method according to an aspect of the presentdisclosure, in the determining of the encoded stream, a determinationmay be made, for each picture included in the encoded stream, as towhether the decoding time obtained for the picture matches generationtiming at which a processing signal (corresponding to the videoprocessing signal explained above) is generated at a cycle defined inadvance, and when the decoding time is determined to match thegeneration timing, the picture may be decoded. For example, the imagedecoding method may further include determining a reciprocal of a framerate at which all the pictures included in the encoded stream aredecoded and displayed to be the cycle defined in advance.

Therefore, as shown in the flowchart of FIG. 10, even if the decodingtimes of the plurality of pictures are not spaced at regular intervals,each of the plurality of pictures can be decoded appropriately at thedecoding time of the picture.

It should be noted that, in each of the exemplary embodiments, eachconstituent element may be implemented with dedicated hardware, or byexecuting a software program appropriate for each constituent element.Each constituent element may be implemented by causing a programexecution unit such as a CPU or a processor to read and execute asoftware program recorded on a recording medium such as a hard disk or asemiconductor memory. In this case, the software that implements imageencoding apparatuses 10 and 100 according to the exemplary embodiment ormodifications causes a computer to execute each step included in theflowchart as illustrated in FIG. 15B. On the other hand, the softwarethat implements image decoding apparatuses 20 and 200 according to theexemplary embodiment or modifications causes a computer to execute eachstep included in the flowchart as illustrated in FIG. 15D.

Second Exemplary Embodiment

A program for implementing a configuration of a motion picture encodingmethod (image encoding method) or a motion picture decoding method(image decoding method) as shown in each of the exemplary embodiments isrecorded on a storage medium, so that the processing as shown in each ofthe exemplary embodiments can be implemented easily in a standalonecomputer system. The storage medium may be any given type of mediumcapable of storing a program, such as a magnetic disk, an optical disk,a magneto-optical disk, an IC (Integrated Circuit) card, or asemiconductor memory.

Now, exemplary applications of a motion picture encoding method (imageencoding method) and a motion picture decoding method (image decodingmethod) as shown in each of the exemplary embodiments and systems usingthem will be further explained. The system is characterized in includingan image encoding decoding apparatus including an image encodingapparatus using the image encoding method and an image decodingapparatus using the image decoding method. The other configurations ofthe systems can be changed as necessary in accordance withcircumstances.

FIG. 16 is a diagram illustrating an entire configuration of contentproviding system ex100 that implements content distribution services. Anarea in which communication services are provided is divided into cellsof a desired size, and base stations ex106, ex107, ex108, ex109, andex110, which are fixed wireless stations, are installed in therespective cells.

In content providing system ex100, various devices, such as computerex111, PDA (Personal Digital Assistant) ex112, camera ex113, mobilephone ex114, game machine ex115, are connected to Internet ex101 viaInternet service provider ex102 and telephone network ex104, and basestations ex106 to ex110.

However, the configuration of content providing system ex100 is notlimited to the configuration as illustrated in FIG. 16. Alternatively,any given combination of the elements may be connected. Each device maybe directly connected to the telephone network ex104 without relying onbase stations ex106 to ex110 which are the fixed wireless stations.Still alternatively, the devices may be directly interconnected via anear field communication or the like.

Camera ex113 is a device capable of capturing motion pictures, such as adigital camcorder. Camera ex116 is a device capable of capturing stillpictures and motion pictures, such as a digital camera. Moreover, mobilephone ex114 may be any of a mobile phone based on GSM (registeredtrademark) (Global System for Mobile Communications) scheme, CDMA (CodeDivision Multiple Access) scheme, W-CDMA (Wideband-Code DivisionMultiple Access) scheme, or LTE (Long Term Evolution) scheme, HSPA (HighSpeed Packet Access); or PHS (Personal Handyphone System); and the like.

In content providing system ex100, camera ex113 or the like is connectedvia base station ex109 and telephone network ex104 to streaming serverex103, so that live streaming or the like is implemented. During livestreaming, encoding processing is performed on content (for example,video and the like of music event) captured by the user using cameraex113 in a manner as explained in each of the exemplary embodiments(that is, camera ex113 functions as the image encoding apparatusaccording to an aspect of the present disclosure), and the encodedcontent is transmitted to streaming server ex103. On the other hand,streaming server ex103 distributes the received content data as a streamto a client that has made a request. Examples of the client includecomputer ex111, PDA ex112, camera ex113, mobile phone ex114, and gamemachine ex115 capable of decoding the data that has been subjected tothe encoding processing. Each device that has received the distributeddata performs the decoding processing on the received data to reproducethe data (that is, the device functions as the image decoding apparatusaccording to an aspect of the present disclosure).

It should be noted that the encoding processing may be performed on thecaptured data by camera ex113, by streaming server ex103 that performstransmission processing of data, or by both of them on aprocessing-sharing basis. Likewise, the decoding processing may beperformed on the distributed data by a client, by streaming serverex103, or by both of them on a processing-sharing basis. Moreover, stilland/or motion picture data captured by not only camera ex113 but alsocamera ex116 may be transmitted via computer ex111 to streaming serverex103. The encoding processing in this case may be performed by any ofcamera ex116, computer ex111, and streaming server ex103, or by all ofthem on a processing-sharing basis.

These pieces of encoding and decoding processing are generally performedby LSI ex500 included in computer ex111 or each device. LSI ex500 may beformed as a single chip or multiple chips. It should be noted thatsoftware for motion picture encoding and decoding may be recorded on anygiven recording medium (such as a CD-ROM, a flexible disk, or a harddisk) that is readable by computer ex111 or the like, and the encodingand decoding processing may be performed by using the software. Further,in a case where mobile phone ex114 is equipped with a camera, motionpicture data obtained by the camera may be transmitted. Motion picturedata at this occasion is data that has been subjected to the encodingprocessing by LSI ex500 included in mobile phone ex114.

Streaming server ex103 may be a plurality of servers or a plurality ofcomputers that process, record, and distribute data in a distributedmanner.

As described above, content providing system ex100 allows the client toreceive and reproduce encoded data. In this manner, content providingsystem ex100 allows the client to receive, decode, and reproduceinformation transmitted by the user in real time, and thus allows a userwho does not have any special rights or equipment to implement personalbroadcasting.

It should be noted that, in addition to the example of content providingsystem ex100, at least one of the motion picture encoding apparatus(image encoding apparatus) and the motion picture decoding apparatus(image decoding apparatus) according to each of the exemplaryembodiments can be incorporated into digital broadcasting system ex200as illustrated in FIG. 17. More specifically, in broadcasting stationex201, multiplexed data obtained by multiplexing music data with videodata is transmitted via a radio wave to communication or satelliteex202. This video data is data encoded in accordance with a motionpicture encoding method explained in each of the exemplary embodiments(more specifically, this video data is data encoded by the imageencoding apparatus according to an aspect of the present disclosure).Broadcasting satellite ex202 having received this data transmits abroadcast radio wave, and home antenna ex204 capable of receivingsatellite broadcasting receives this radio wave. An apparatus such astelevision set (receiver) ex300 or set top box (STB) ex217 decodes andreproduces the received multiplexed data (that is, the apparatusfunctions as the image decoding apparatus according to an aspect of thepresent disclosure).

The motion picture decoding apparatus or the motion picture encodingapparatus as shown in each of the exemplary embodiments can also beimplemented in reader/recorder ex218 for reading and decodingmultiplexed data recorded on recording medium ex215 such as DVD or BD;or encoding a video signal and in some cases, multiplexing the data witha music signal and writing the multiplexed data on recording mediumex215. In this case, the reproduced video signal is displayed on monitorex219, and the video signal can be reproduced by another apparatus orsystem using recording medium ex215 having the multiplexed data recordedthereon. Alternatively, the motion picture decoding apparatus may beimplemented in set top box ex217 connected to cable ex203 for a cabletelevision set or antenna ex204 for satellite/terrestrial wavebroadcasting, and the video signal may be displayed on monitor ex219 ofthe television set. At this occasion, the motion picture decodingapparatus may be incorporated into the television set instead of the settop box.

FIG. 18 is a diagram illustrating television set (receiver) ex300 thatemploys the motion picture decoding method and the motion pictureencoding method explained in each of the exemplary embodiments.Television set ex300 includes tuner ex301 for obtaining or outputtingmultiplexed data obtained by multiplexing video data with audio data viaantenna ex204, cable ex203, or the like that receives the broadcast,modulator/demodulator ex302 for demodulating the received multiplexeddata or modulating multiplexed data to be transmitted to the outside,and multiplexer/demultiplexer ex303 for demultiplexing the demodulatedmultiplexed data into video data and audio data or multiplexing thevideo data and the audio data encoded by signal processor ex306.

In addition, television set ex300 includes signal processor ex306 andoutput unit ex309. Signal processor ex306 includes audio signalprocessor ex304 that decodes audio data or encodes information aboutaudio data, and video signal processor ex305 that decodes video data orencodes information about video data (video signal processor ex305functions as an image encoding apparatus or an image decoding apparatusaccording to an aspect of the present disclosure). Output unit ex309includes speaker ex307 that outputs a decoded audio signal and displayex308, such as a display, that displays a decoded video signal.Television set ex300 further includes interface unit ex317 includingoperation input ex312 that accepts input of user operation. Televisionset ex300 further includes controller ex310 that controls each unit inan integrated manner, and power supply circuit ex311 that supplieselectric power to each unit. Interface unit ex317 may include not onlyoperation input ex312 but also bridge ex313 to be connected to anexternal device such as reader/recorder ex218, slot ex314 to whichrecording medium ex216 such as SD card can be connected, driver ex315for connection to an external recording medium such as a hard disk,modem ex316 for connection to a telephone network, and the like. Itshould be noted that recording medium ex216 can electrically recordinformation with a non-volatile/volatile semiconductor memory elementstored therein. The individual units of television set ex300 areconnected to one another via a synchronization bus.

First, a configuration will be explained in which television set ex300decodes and reproduces multiplexed data obtained from the outside withantenna ex204 and the like. Television set ex300 receives a useroperation from remote controller ex220 and the like, andmultiplexer/demultiplexer ex303 demultiplexes multiplexed datademodulated by modulator/demodulator ex302 on the basis of controlperformed by controller ex310 having a CPU and the like. Further, intelevision set ex300, audio signal processor ex304 decodes the separatedaudio data, and video signal processor ex305 decodes the separated videodata by using a decoding method explained in each of the exemplaryembodiments. The decoded audio signal and the video signal are output tothe outside from the output unit ex309. When the audio signal and thevideo signal are output, the audio signal and the video signal may betemporarily accumulated in buffers ex318 and ex319 or the like such thatthe audio signal and the video signal are reproduced in synchronizationwith each other. Instead of broadcasting and the like, television setex300 may read multiplexed data from recording media ex215 and ex216such as a magnetic/optical disk and an SD card. Subsequently, aconfiguration will be explained in which television set ex300 encodesthe audio signal and the video signal, and transmits the encoded signalsto the outside or writes the encoded signals on a recording medium orthe like. Television set ex300 receives a user operation from remotecontroller ex220 or the like, and on the basis of control performed bycontroller ex310, audio signal processor ex304 encodes the audio signal,and video signal processor ex305 encodes the video signal by using theencoding method explained in each of the exemplary embodiments. Theencoded audio signal and the video signal are multiplexed bymultiplexer/demultiplexer ex303, and the multiplexed signal is output tothe outside. When the audio signal and the video signal are multiplexed,the audio signal and the video signal may be temporarily accumulated inbuffers ex320 and ex321 or the like such that the audio signal and thevideo signal are synchronized with each other. It should be noted thatmultiple buffers may be provided as illustrated as buffers ex318, ex319,ex320 and ex321; or one or more buffers may be shared. Further, otherthan the buffers illustrated in the drawings, for example, data may bestored in a buffer serving as a buffering member for avoiding anoverflow or underflow in the system between modulator/demodulator ex302,multiplexer/demultiplexer ex303, or the like.

Television set ex300 may have a configuration of receiving an AV inputof a microphone and a camera in addition to the configuration ofobtaining audio data and video data from broadcasting and the like and arecording medium and the like, and may perform encoding processing onthe data obtained therefrom. It should be noted that, in this case,television set ex300 is explained as a configuration capable ofperforming the encoding processing, multiplexing, and outputting tooutside. Alternatively, television set ex300 may be a configurationincapable of performing these processing, and only capable of performingthe reception, decoding processing, and outputting to outside.

In a case where reader/recorder ex218 reads or writes multiplexed datafrom or to a recording medium, the decoding processing or the encodingprocessing may be performed by any of television set ex300 andreader/recorder ex218, or by both television set ex300 andreader/recorder ex218 on a processing-sharing basis.

FIG. 19 illustrates an example of a configuration of informationreproducing/recording unit ex400 in a case where data is read or writtenfrom or to an optical disk. Information reproducing/recording unit ex400includes elements ex401, ex402, ex403, ex404, ex405, ex406, and ex407explained below. Optical head ex401 irradiates a recording surface ofrecording medium ex215, which is an optical disk, with a laser spot towrite information thereon; and detects reflected light from therecording surface of the recording medium ex215 to read information.Modulation recorder ex402 electrically drives a semiconductor laserincluded in optical head ex401 to modulate the laser light according tothe recorded data. Demodulation reproducer ex403 amplifies a reproducedsignal obtained by electrically detecting reflected light from therecording surface by a photodetector included in optical head ex401, andseparates and demodulates signal components recorded on recording mediumex215, and reproduces necessary information. Buffer ex404 temporarilyholds information to be recorded on recording medium ex215 andinformation reproduced from recording medium ex215. Disk motor ex405rotates recording medium ex215. Servo controller ex406 performs trackingprocessing of the laser spot by moving optical head ex401 topredetermined information track while controlling rotation and drivingof disk motor ex405. System controller ex407 controls the entireinformation reproducing/recording unit ex400. The above reading andwriting processing is implemented when system controller ex407 usesvarious pieces of information held in buffer ex404, generates and addsnew information as necessary, causes modulation recorder ex402,demodulation reproducer ex403, and servo controller ex406 to performcooperation operation, and perform recording and reproduction ofinformation via optical head ex401. System controller ex407 includes,for example, a microprocessor and executes these processing by executinga reading or writing program.

Although optical head ex401 that irradiates the recording surface with alaser spot has been described above, optical head ex401 may include aconfiguration of performing high density recording by using near fieldlight.

FIG. 20 is a schematic diagram of recording medium ex215 which is anoptical disk. On the recording surface of recording medium ex215,guiding grooves (groups) are formed in a spiral form, and addressinformation representing an absolute position on the disk is recorded inadvance in information track ex230 by using a change in the shape of thegroove. This address information includes information for identifyingthe position of recording block ex231 which is a unit for recordingdata, and when the apparatus for performing recording and reproductionreproduces information track ex230 and reads the address information,the recording block can be identified. Recording medium ex215 includesdata recording area ex233, inner circumference area ex232, and externalcircumference area ex234. An area used to record the user data is datarecording area ex233, and inner circumference area ex232 and externalcircumference area ex234 that are disposed at the inner side or theouter side of data recording area ex233 are used for the identificationpurpose other than recording of the user data. Informationreproducing/recording unit ex400 reads and writes encoded audio data,video data, or multiplexed data obtained by multiplexing the data fromand to data recording area ex233 of such recording medium ex215.

The description has been given using a one layer optical disk such asDVD or BD as an example, but the optical disk used is not limitedthereto. An optical disk having a multi-layer structure and capable ofrecording on a part other than the front surface may be used.Alternatively, it may be an optical disk having a structure formulti-dimensional recording and reproduction, for example, recordinginformation by using color lights having various different wavelengthsin the same location of the disk, and recording a layer of differentinformation in various angles.

In digital broadcasting system ex200, vehicle ex210 equipped withantenna ex205 may receive data from satellite ex202 or the like, and adisplay device such as car navigation ex211 mounted on vehicle ex210 mayreproduce a motion picture. For example, it should be noted that theconfiguration of car navigation ex211 may be considered to be aconfiguration including a GPS reception unit in addition to theconfiguration as illustrated in FIG. 18, and the same applies tocomputer ex111, mobile phone ex114, and the like.

FIG. 21A is a diagram illustrating mobile phone ex114 using the motionpicture decoding method and the motion picture encoding method explainedin the exemplary embodiment. Mobile phone ex114 includes antenna ex350for transmitting and receiving a radio wave to and from base stationex110; camera unit ex365 capable of capturing video and still pictures;and display ex358, such as a liquid crystal display, for displayingvideo captured by camera unit ex365 and data obtained by decoding videoand the like received by antenna ex350. Mobile phone ex114 furtherincludes a body having operation key unit ex366; audio output unit ex357such as a speaker for outputting audio; audio input ex356 such as amicrophone for inputting audio; memory ex367 that stores encoded data ordecoded data such as captured video, captured still pictures, recordedaudio, or received video, received still pictures, and received emails;and slot ex364 which is an interface to a recording medium whichsimilarly stores data thereon.

Further, an example of a configuration of mobile phone ex114 will beexplained with reference to FIG. 21B. Mobile phone ex114 includes powersupply circuit ex361, operation input controller ex362, video signalprocessor ex355, camera interface unit ex363, LCD (Liquid CrystalDisplay) controller ex359, modulation/demodulation unit ex352,multiplexer/demultiplexer ex353, audio signal processor ex354, slotex364, and memory ex367 are connected with each other via bus ex370 tomain controller ex360 that controls each unit of the body having displayex358 and operation key unit ex366 in an integrated manner.

When an on-hook/power key is turned on through a user operation, powersupply circuit ex361 activates mobile phone ex114 to cause mobile phoneex114 to be in operable state by supplying electric power to each unitfrom the battery pack.

On the basis of control performed by main controller ex360 having a CPU,a ROM, a RAM, and the like, mobile phone ex114 causes audio signalprocessor ex354 to convert an audio signal collected by audio inputex356 in audio voice call mode into a digital audio signal, and causesmodulation/demodulation unit ex352 to perform spread spectrum processingthe digital audio signal, and causes transmission/reception unit ex351to perform digital analog conversion processing and frequency conversionprocessing on the digital audio signal and thereafter transmits thesignal via antenna ex350. Mobile phone ex114 amplifies received datareceived via antenna ex350 in audio voice call mode and performsfrequency conversion processing and analog digital conversion processingon the data, and causes modulation/demodulation unit ex352 to performinverse spread spectrum processing on the data, and causes audio signalprocessor ex354 to convert it into an analog audio signal, andthereafter outputs the analog audio signal from audio output unit ex357.

Further, in a case where an e-mail is transmitted in data communicationmode, text data of an e-mail which is input by operation with operationkey unit ex366 and the like of the body are transmitted via operationinput controller ex362 to main controller ex360. Main controller ex360causes modulation/demodulation unit ex352 to perform spread spectrumprocessing on text data and causes transmission/reception unit ex351 toperform digital analog conversion processing and frequency conversionprocessing on the text data, and thereafter transmits the data viaantenna ex350 to base station ex110. In a case where an e-mail isreceived, substantially opposite processing is performed on the receiveddata, and the data is output to display ex358,

In a case where video, still picture, or video and audio are transmittedin data communication mode, video signal processor ex355 compresses andencodes the video signal provided from camera unit ex365 in accordancewith a motion picture encoding method indicated by each of the exemplaryembodiments (that is, video signal processor ex355 functions as an imageencoding apparatus according to an aspect of the present disclosure),and transmits the encoded video data to multiplexer/demultiplexer ex353.Audio signal processor ex354 encodes the audio signal collected by audioinput ex356 while camera unit ex365 captures video, still pictures, andthe like, and transmits the encoded audio data tomultiplexer/demultiplexer ex353.

Multiplexer/demultiplexer ex353 multiplexes the encoded video dataprovided from video signal processor ex355 and the encoded audio dataprovided from audio signal processor ex354 in accordance with apredetermined method, and causes modulation/demodulation unit(modulation/demodulation circuit) ex352 to perform spread spectrumprocessing on the multiplexed data obtained as a result, and causestransmission/reception unit ex351 to perform digital analog conversionprocessing and frequency conversion processing on the multiplexed data,and thereafter, transmits the data via antenna ex350.

In a case where data of a motion picture file linked to a home page andthe like is received in data communication mode, or in a case where ane-mail attached with video and/or audio is received,multiplexer/demultiplexer ex353 demultiplexes multiplexed data to dividethe multiplexed data into the bit stream of the video data and the bitstream of the audio data in order to decode the multiplexed datareceived via antenna ex350, and provides the encoded video data viasynchronization bus ex370 to video signal processor ex355, and providesthe encoded audio data to audio signal processor ex354. Video signalprocessor ex355 decodes the video signal by decoding the video signal inaccordance with a motion picture decoding method corresponding to amotion picture encoding method indicated by each of the exemplaryembodiments (that is, video signal processor ex355 functions as an imagedecoding apparatus according to an aspect of the present disclosure), sothat, for example, video and still pictures included in a motion picturefile linked to a home page are displayed on display ex358 via LCDcontroller ex359. Audio signal processor ex354 decodes the audio signal,and audio output unit ex357 outputs the audio.

Like television set ex300, the terminal of mobile phone ex114 and thelike is considered to be in three types of implementation forms, thatis, not only a transmission and reception type terminal having both ofan encoding device and a decoding device, but also a transmissionterminal having only an encoding device and a reception terminal havingonly a decoding device. Further, the case has been described in whichmultiplexed data obtained by multiplexing music data with video data arereceived and transmitted in digital broadcasting system ex200.Alternatively, the multiplexed data may be data in which text datarelated to the video is multiplexed other than audio data or video dataalone may be used instead of the multiplexed data.

As described above, the motion picture encoding method or the motionpicture decoding method as shown in each of the exemplary embodimentscan be used for any one of the devices and the systems explained above.In such a way, the effects explained in each of the exemplaryembodiments can be obtained.

The present disclosure is not limited to the exemplary embodimentexplained above, and various modifications and changes can be madewithout deviating from the scope of the present disclosure.

Third Exemplary Embodiment

Video data can also be generated by appropriately switching, asnecessary, the motion picture encoding method or the apparatus as shownin each of the exemplary embodiments and the motion picture encodingmethod or the apparatus based on a different standard such as MPEG-2,MPEG4-AVC, or VC-1.

In this case, in a case where a plurality of pieces of video data basedon different standards are generated, it is necessary to select adecoding method corresponding to each of the standards at the time ofdecoding. However, because which standard the video data to be decodedis based on is not identifiable, there is a problem in that it isimpossible to select an appropriate decoding method.

In order to solve this problem, the multiplexed data obtained bymultiplexing audio data and the like with video data is configured toinclude identification information indicating which standard the videodata are based on. A specific configuration of multiplexed dataincluding video data generated by the motion picture encoding method orthe apparatus as shown in each of the exemplary embodiments will beexplained below. The multiplexed data is a digital stream in MPEG-2transport stream format.

FIG. 22 is a diagram illustrating a configuration of multiplexed data.As illustrated in FIG. 22, the multiplexed data is obtained bymultiplexing one or more of the video stream, the audio stream, thepresentation graphics stream (PG), and the interactive graphics stream.The video stream represents main video and sub video of a movie, theaudio stream (IG) represents main audio portion of the movie and subaudio mixed with the main audio, and the presentation graphics streamrepresents subtitles of the movie. In this case, the main videoindicates a normal video displayed on a screen, and the sub videoindicates video displayed on a small screen in the main video. Theinteractive graphics stream indicates an interactive screen generated byarranging GUI components on the screen. The video stream is encoded bythe motion picture encoding method or the apparatus as shown in each ofthe exemplary embodiments and the motion picture encoding method or theapparatus based on standards such as conventional MPEG-2, MPEG4-AVC,VC-1, or the like. The audio stream is encoded in accordance withmethods such as Dolby AC-3, Dolby Digital Plus, MLP, DTS, DTS-HD, orlinear PCM.

Each stream included in the multiplexed data is identified by a PID. Forexample, 0x1011 is allocated to the video stream used for the video ofthe movie, 0x1100 to 0x111F are allocated to the audio stream, 0x1200 to0x121F are allocated to the presentation graphics, 0x1400 to 0x141F areallocated to the interactive graphics stream, and 0x1B00 to 0x1B1F areallocated to the video stream used for the sub video of the movie, and0x1A00 to 0x1A1F are allocated to the audio stream used for the subaudio mixed with the main audio.

FIG. 23 is a diagram schematically illustrating how the multiplexed datais multiplexed. First, video stream ex235 including a plurality of videoframes and audio stream ex238 including a plurality of audio frames areconverted into PES packet sequences ex236 and ex239, and converted intoTS packets ex237 and ex240. Likewise, the data of presentation graphicsstream ex241 and the interactive graphics ex244 are converted into PESpacket sequences ex242 and ex245, and further converted into TS packetsex243 and ex246. The multiplexed data ex247 is formed by multiplexingthese TS packets into a single stream.

FIG. 24 illustrates, in more detail, how the video stream is stored inthe PES packet sequence. In FIG. 24, the first stage illustrates a videoframe sequence of the video stream. The second stage illustrates a PESpacket sequence. As shown by arrows yy1, yy2, yy3, and yy4 of FIG. 24,the I picture, the B picture, the P picture which are a plurality ofVideo Presentation Units in the video stream are divided for eachpicture, and are stored in the payloads of the PES packets. Each PESpacket has a PES header, and the PES header stores a PTS (PresentationTime-Stamp) which is a display time of a picture and a DTS (DecodingTime-Stamp) which is a decoding time of a picture.

FIG. 25 illustrates a format of a TS packet ultimately written tomultiplexed data. The TS packet is a packet having a fixed length of 188Bytes constituted by a TS header of 4 Bytes having information about aPID and the like for identifying a stream and a TS payload of 184 Bytesfor storing data, and the PES packet is divided and stored in the TSpayload. In the case of BD-ROM, TP_Extra_Header of 4 Bytes is given tothe TS packet, so that a source packet of 192 Bytes is made and writtento multiplexed data. In TP_Extra_Header, information such as ATS(Arrival_Time_Stamp) is described. ATS indicates a transfer start timefor a PID filter of a decoder of the TS packet. In the multiplexed data,the source packets are arranged as shown in the lower stage of FIG. 25,and a number that is increased from the head of the multiplexed data iscalled an SPN (source packet number).

The TS packets included in the multiplexed data include not only thestreams such as video, audio, subtitle, and the like but also PAT(Program Association Table), PMT (Program Map Table), PCR (Program ClockReference), and the like. The PAT indicates what is the PID of the PMTused in the multiplexed data, and the PID of the PAT itself isregistered as zero. The PMT has the PIDs of the streams such as video,audio, subtitle, and the like included in the multiplexed data andattribute information about the stream corresponding to each PID, andincludes various kinds of descriptors about the multiplexed data. Thedescriptor includes copy control information for designating permissionor prohibition of copy of the multiplexed data. In order to maintainsynchronization between the ATC (Arrival Time Clock) which is thetemporal axis of the ATS and the STC (System Time Clock) which is thetemporal axis of the PTS and the DTS, the PCR has information about theSTC time corresponding to the ATS when the PCR packet is transferred tothe decoder.

FIG. 26 is a diagram for explaining the data structure of the PMT indetail. Leading picture of the PMT, a PMT header describing the lengthof data included in the PMT is disposed. After the PMT header, multipledescriptors about the multiplexed data are disposed. The above copycontrol information and the like is described as the descriptor. Afterthe descriptor, multiple pieces of stream information about the streamsincluded in the multiplexed data are disposed. The stream information ismade up of a stream type for identifying a compression codec and thelike of the stream, a PID of the stream, and a stream descriptordescribing attribute information about the stream (such as a frame rateand an aspect ratio). There are as many stream descriptors as the numberof streams existing in the multiplexed data.

In the case where the multiplexed data is recorded on a recording mediumor the like, the multiplexed data is recorded together with themultiplexed data information file.

As illustrated in FIG. 27, the multiplexed data information file ismanagement information about the multiplexed data, and corresponds tothe multiplexed data in one-to-one manner, and is made up of multiplexeddata information, stream attribute information, and an entry map.

As illustrated in FIG. 27, the multiplexed data information is made upof a system rate, a playback start time, and a playback end time. Thesystem rate indicates a maximum transfer rate of multiplexed data to aPID filter of a system target decoder explained later. The interval ofthe ATS included in the multiplexed data is set to be equal to or lessthan the system rate. The playback start time is set to a PTS of a videoframe leading picture of the multiplexed data, and the playback end timeis set to a value obtained by adding a playback interval of one frame tothe PTS of the video frame at the end of the multiplexed data.

As illustrated in FIG. 28, in the stream attribute information,attribute information about each stream included in the multiplexed datais registered for each PID. The attribute information has informationthat is different for each of the video stream, the audio stream, thepresentation graphics stream, and the interactive graphics stream. Thevideo stream attribute information has information such as what kind ofcompression codec is used to compress the video stream, what is theresolution of each of the picture data constituting the video stream,what is the aspect ratio, and what is the frame rate. The audio streamattribute information has information such as what kind of compressioncodec is used to compress the audio stream, how many channels areincluded in the audio stream, what language is supported, and what isthe sampling frequency. The above information is used to initialize adecoder before the player performs reproduction.

In the present exemplary embodiment, from among the multiplexed data, astream type included in a PMT is used. In a case where the multiplexeddata is recorded on the recording medium, the video stream attributeinformation included in the multiplexed data information is used. Morespecifically, in the motion picture encoding method or the apparatus asshown in each of the exemplary embodiments, a step or means is providedto set unique information indicating video data generated by the motionpicture encoding method or the apparatus as shown in each of theexemplary embodiments for the stream type or the video stream attributeinformation included in the PMT. According to this configuration, videodata generated by the motion picture encoding method or the apparatus asshown in each of the exemplary embodiments and video data based onanother standard can be identified.

FIG. 29 illustrates steps included in the motion picture decoding methodaccording to the present exemplary embodiment. In step exS100, thestream type included in the PMT or the video stream attributeinformation included in the multiplexed data information is obtainedfrom the multiplexed data. Subsequently, in step exS101, a determinationis made as to whether the stream type or the video stream attributeinformation indicates multiplexed data generated by the motion pictureencoding method or the apparatus as shown in each of the exemplaryembodiments. Then, in a case where the stream type or the video streamattribute information is determined to be generated by the motionpicture encoding method or the apparatus as shown in each of theexemplary embodiments, decoding is performed by the motion picturedecoding method as shown in each of the exemplary embodiments in stepexS102. In a case where the stream type or the video stream attributeinformation indicates that it is based on standards such as conventionalMPEG-2, MPEG4-AVC, or VC-1, the decoding is performed in accordance withthe motion picture decoding method based on the conventional standard instep exS103.

As described above, by setting a new unique value for the stream type orthe video stream attribute information, a determination can be made asto whether the decoding can be performed by the motion picture decodingmethod or the apparatus as shown in each of the exemplary embodimentswhen the decoding is performed. Therefore, even in a case wheremultiplexed data based on different standards is input, an appropriatedecoding method or apparatus can be selected, and therefore, decodingcan be performed without causing any error. The motion picture encodingmethod or the apparatus, or the motion picture decoding method or theapparatus as shown in the present exemplary embodiment can also be usedfor any of the devices and the systems explained above.

Fourth Exemplary Embodiment

The motion picture encoding method and the apparatus and the motionpicture decoding method and the apparatus as shown in each of theexemplary embodiments are typically implemented using an LSI which is anintegrated circuit. FIG. 30 illustrates an example of a configuration ofLSI ex500 which is formed as one chip. LSI ex500 includes elementsex501, ex502, ex503, ex504, ex505, ex506, ex507, ex508, and ex509explained below, and each element is connected via bus ex510. Powersupply circuit ex505 provides electric power to each unit to activateeach unit in an operable state in a case where the power supply is inthe ON state.

For example, in a case where the encoding processing is performed, LSIex500 inputs an AV signal from microphone ex117, camera ex113, and thelike with AV I/O ex509 on the basis a control performed by controllerex501 having CPU ex502, memory controller ex503, stream controllerex504, driving frequency controller ex512, and the like. The AV signalwhich has been input is temporarily accumulated in external memory ex511such as an SDRAM. On the basis of control performed by controller ex501,the accumulated data is divided multiple times as necessary inaccordance with the amount of processing and the processing speed, andare sent to signal processor ex507, and encoding of the audio signaland/or encoding of the video signal are performed in signal processorex507. In this case, the encoding processing of the video signal is theencoding processing explained in each of the exemplary embodiments.Signal processor ex507 further performs processing, for example,multiplexing encoded audio data and encoded video data in some cases,and outputs the data from stream I/O ex506 to the outside. Themultiplexed data thus output is transmitted to base station ex107, orwritten to recording medium ex215. It should be noted that, whenmultiplexing, the audio data and the video data are may be temporarilyaccumulated in buffer ex508 such that these pieces of data aresynchronized with each other.

In the case, memory ex511 is explained as a configuration providedoutside of LSI ex500. Alternatively, memory ex511 may be configured tobe included in the inside of LSI ex500. The number of buffers ex508 isnot limited to one and a plurality of buffers may be provided. LSI ex500may be formed as one chip or multiple chips.

In the explanation, controller ex501 includes CPU ex502, memorycontroller ex503, stream controller ex504, driving frequency controllerex512, and the like, but the configuration of controller ex501 is notlimited to this configuration. For example, signal processor ex507 maybe configured to further include a CPU. By additionally providing a CPUin the inside of signal processor ex507, the processing speed can befurther improved. As another example, CPU ex502 may be configured toinclude signal processor ex507 or, for example, an audio signalprocessor which is a part of signal processor ex507. In such case,controller ex501 is configured to include signal processor ex507 or CPUex502 which is a part thereof.

In this case, LSI is employed, but depending on the degree ofintegration, it may also be referred to as an IC, a system LSI, a superLSI, and an ultra LSI.

The method of making integrated circuit is not limited to the LSI.Alternatively, it may be implemented using with a dedicated circuit or agenerally-purpose processor. An FPGA (Field Programmable Gate Array)that can be programmed after an LSI is produced or a reconfigurableprocessor that can reconfigure connection and settings of the circuitcells in the LSI may also be used.

Furthermore, when there is a progress made in the semiconductortechnique or with the advent of the technique of making an integrationcircuit that replaces the LSI with another accompanying technique, it isto be understood that the functional blocks may be integrated by usingsuch techniques. An application of biotechnology and the like isconsidered to be possible.

Fifth Exemplary Embodiment

The amount of processing is considered to be higher in a case wherevideo data generated by the motion picture encoding method or theapparatus as shown in each of the exemplary embodiments is decoded thanin a case where video data based on standards such as conventionalMPEG-2, MPEG4-AVC, or VC-1 are decoded. For this reason, in LSI ex500,it is necessary to set a driving frequency higher than a drivingfrequency of CPU ex502 for decoding video data based on conventionalstandards. However, when the driving frequency is set at a higher level,there is a problem in that the consumed electric power increases.

In order to solve this problem, a motion picture decoding apparatus suchas television set ex300 or LSI ex500 is configured to identify astandard which the video data is based on, and to switch between thedriving frequencies in accordance with the standard. FIG. 31 illustratesa configuration ex800 in the present exemplary embodiment. Drivingfrequency switching unit ex803 sets a higher driving frequency in a casewhere the video data is generated by the motion picture encoding methodor the apparatus as shown in each of the exemplary embodiments. Then,driving frequency switching unit ex803 instructs decoding processorex801 executing the motion picture decoding method as shown in each ofthe exemplary embodiments to decode video data. On the other hand, in acase where the video data is video data based on the conventionalstandard, driving frequency switching unit ex803 sets the drivingfrequency is set to be lower than a case where the video data isgenerated by the motion picture encoding method or the apparatus asshown in each of the exemplary embodiments. Then, driving frequencyswitching unit ex803 instructs decoding processor ex802 based on theconventional standard to decode the video data.

More specifically, driving frequency switching unit ex803 includes CPUex502 and driving frequency controller ex512 of FIG. 30. Decodingprocessor ex801, decoding processor ex801 executing the motion picturedecoding method as shown in each of the exemplary embodiments anddecoding processor ex802 based on the conventional standards correspondto signal processor ex507 of FIG. 30. CPU ex502 identifies whichstandard the video data is based on. Then, driving frequency controllerex512 sets the driving frequency on the basis of the signal from CPUex502. On the basis of the signal from CPU ex502, signal processor ex507decodes the video data. In this case, in order to identify video data,for example, the identification information described in the thirdexemplary embodiment is considered to be used. The identificationinformation is not limited to one described in the third exemplaryembodiment, and may be information that can identify which standard thevideo data is based on. For example, in a case where which standard thevideo data is based on can be identified on the basis of an externalsignal for identifying whether the video data are used for a televisionset or used for a disk, the identification can be made on the basis ofsuch external signal. The selection of the driving frequency of CPUex502 is considered to be performed on the basis of, for example, alookup table in which a standard of video data as illustrated in FIG. 33and a driving frequency are associated with each other. When the lookuptable is stored in an internal memory of the LSI or buffer ex508, CPUex502 can select the driving frequency by referring to the lookup table.

FIG. 32 illustrates steps for performing the method of the presentexemplary embodiment. First, in step exS200, signal processor ex507obtains identification information from the multiplexed data.Subsequently, in step exS201, CPU ex502 identifies, on the basis of theidentification information, whether or not the video data is generatedby the encoding method or the apparatus as shown in each of theexemplary embodiments. In a case where the video data is determined tobe generated by the encoding method or the apparatus as shown in each ofthe exemplary embodiments, CPU ex502 sends a signal for setting a higherdriving frequency to driving frequency controller ex512 in step exS202.Then, with driving frequency controller ex512, higher driving frequencyis set. On the other hand, in a case where the video data indicatesvideo data based on standards such as conventional MPEG-2, MPEG4-AVC, orVC-1, CPU ex502 sends a signal for setting a lower driving frequency todriving frequency controller ex512 in step exS203. Then, drivingfrequency controller ex512 sets a driving frequency lower than that fora case where the video data is generated by the encoding method or theapparatus as shown in each of the exemplary embodiments.

Further, when a voltage given to the apparatus including LSI ex500 orLSI ex500 is changed in synchronization with switching of the drivingfrequency, the effect of saving the electric power can be furtherimproved. For example, in a case where the driving frequency is set tobe low, the voltage given to the apparatus including LSI ex500 or LSIex500 is considered to be accordingly set to be lower than that for thecase where the driving frequency is set to be higher.

In the setting method of the driving frequency, the driving frequencymay be set to be higher in a case where the amount of processing duringdecoding is high, and the driving frequency may be set to be lower in acase where the amount of processing during decoding is low, and thesetting method of the driving frequency is not limited to the settingmethod explained above. For example, in a case where the amount ofprocessing for decoding the video data based on the MPEG4-AVC standardis more than the amount of processing for decoding the video datagenerated by the motion picture encoding method or the apparatus asshown in each of the exemplary embodiments, the setting of the drivingfrequency may be made oppositely to the case described above.

Further, the setting method of the driving frequency is not limited tothe configuration for reducing the driving frequency. For example, in acase where the identification information indicates video data generatedby the motion picture encoding method or the apparatus as shown in eachof the exemplary embodiments, a voltage given to the apparatus includingLSI ex500 or LSI ex500 is considered to be set higher, and, in a casewhere the identification information indicates video data based onstandards of conventional MPEG-2, MPEG4-AVC, VC-1, or the like, thevoltage given to the apparatus including LSI ex500 or LSI ex500 isconsidered to be set lower. In another example, in a case where theidentification information indicates video data generated by the motionpicture encoding method or the apparatus as shown in each of theexemplary embodiments, the driving of CPU ex502 is considered not to bestopped, and in a case where the identification information indicates svideo data based on standards of conventional MPEG-2, MPEG4-AVC, VC-1,or the like, there is a margin in the processing, and therefore, drivingof CPU ex502 is considered to be temporarily stopped. If there is amargin in the processing even in the case where the identificationinformation indicates video data generated by the motion pictureencoding method or the apparatus as shown in each of the exemplaryembodiments, driving of CPU ex502 is considered to be stoppedtemporarily. In this case, the stop time can be set to be shorter thanthat for the case where the identification information indicates s videodata based on standards of conventional MPEG-2, MPEG4-AVC, VC-1, or thelike.

As described above, by switching the driving frequency in accordancewith the standard which the video data is based on, the consumedelectric power can be reduced. In a case where an apparatus includingLSI ex500 or LSI ex500 is driven with a battery, the lifetime of thebattery can be increased in accordance with the lower electric powerconsumption.

Sixth Exemplary Embodiment

In some cases, a plurality of pieces of video data based on differentstandards may be input into the device and the system explained above,such as a television set and a mobile phone. As described above, inorder to allow decoding even in a case where a plurality of pieces ofvideo data based on different standards are input, signal processorex507 of LSI ex500 needs to support the plurality of standards. However,when signal processor ex507 supporting the standards is usedindividually, the size of the circuit of LSI ex500 increases, and thereis a problem in that the cost increases.

In order to solve this problem, a decoding processor for executing themotion picture decoding method as shown in each of the exemplaryembodiments and a decoding processor based on standards such asconventional MPEG-2, MPEG4-AVC, VC-1, or the like are configured to bepartially made to be shared. An example of this configuration is shownin ex900 of FIG. 34A. For example, in the motion picture decoding methodas shown in each of the exemplary embodiments and the motion picturedecoding method based on MPEG4-AVC standard, some of the contents of theprocessing are the same in processing such as entropy encoding, inversequantization, deblocking filtering, and motion compensation. For thesame contents of the processing, decoding processor ex902 supporting theMPEG4-AVC standard is considered to be shared, and for the othercontents of the processing which does not support the MPEG4-AVC standardand which is unique to an aspect of the present disclosure, dedicateddecoding processor ex901 is considered to be used. To share the decodingprocessor, the decoding processor for executing the motion picturedecoding method as shown in each of the exemplary embodiments may beconfigured to be shared for the same contents of the processing, and thededicated decoding processor may be configured to be used for thecontents of the processing unique to the MPEG4-AVC standard.

Another example for partially sharing the processing is shown in ex1000of FIG. 34B. In this example, dedicated decoding processor ex1001supporting the contents of the processing unique to an aspect of thepresent disclosure, dedicated decoding processor ex1002 supporting thecontents of the processing unique to another conventional standard, andshared decoding processor ex1003 supporting the contents of theprocessing which are common to the motion picture decoding methodaccording to an aspect of the present disclosure and the motion picturedecoding method of another conventional standard are configured to beused. In this case, dedicated decoding processors ex1001 and ex1002 arenot necessarily specialized in the contents of the processing unique toan aspect of the present disclosure or another conventional standard,and may be capable of executing other generally-purpose processing. Theconfiguration of the present exemplary embodiment may be implementedusing LSI ex500.

As described above, the decoding processor is made to be shared for thecontents of the processing that are common to the motion picturedecoding method according to an aspect of the present disclosure and themotion picture decoding method of a conventional standard, so that thesize of the circuit of the LSI can be reduced, and the cost can bereduced.

As described above, the image encoding method and the image decodingmethod according to an aspect or a plurality of aspects have beexplained on the basis of the exemplary embodiments, but the presentdisclosure is not limited to the exemplary embodiments. An exemplaryembodiment made by applying various kinds of modifications that areconceived by a person skilled in the art to the present exemplaryembodiment and a form structured by combining constituent elementsaccording to different exemplary embodiments may be included in thescope of an aspect or a plurality of aspects as long as they do notdeviate from the gist of the present disclosure.

The present disclosure can be applied to, for example, an image encodingapparatus, an image decoding apparatus, and the like, and morespecifically, the present disclosure can be used for information displaydevices, image capture devices, and the like such as a television set, adigital video recorder, a car navigation system, a mobile phone, adigital still camera, and a digital camcorder.

What is claimed is:
 1. An image encoding method for encoding a motionpicture for each picture which belongs to any one of a plurality oflayers, without referring to another picture which belongs to a layerhigher than the layer to which the picture belongs, the image encodingmethod comprising: determining respective decoding times of a pluralityof pictures included in the motion picture such that decoding times of aplurality of lower layer pictures which are a portion of the pluralityof pictures included in the motion picture and which do not belong to ahighest layer of the plurality of layers are spaced at regularintervals, and that decoding timing for each of the plurality of lowerlayer pictures is identical between a case where the plurality ofpictures included in the motion picture which has been encoded aredecoded and a case where only the plurality of lower layer pictures aredecoded; encoding each of the plurality of pictures included in themotion picture in accordance with an encoding order according to thedetermined respective decoding times; and generating an encoded streamincluding the plurality of encoded pictures and the determinedrespective decoding times for the plurality of pictures, wherein adisplay order of the plurality of pictures is different from a decodingorder of the plurality of pictures.
 2. The image encoding methodaccording to claim 1, wherein, in the determining of the respectivedecoding times, a decoding time of each of a plurality of uppermostlayer pictures which are another portion of the plurality of picturesincluded in the motion picture and which belong to the highest layer isdetermined to be between the respective decoding times of the pluralityof lower layer pictures.
 3. The image encoding method according to claim2, wherein, the respective decoding time of each of the plurality ofpictures included in the motion picture is determined such that twicethe time period of an interval of decoding times of an uppermost layerpicture and a lower layer picture which are continuous in the decodingorder is equal to the regular interval, the uppermost layer picture andthe lower layer picture are one of the plurality of uppermost layerpictures and one of the plurality of lower layer pictures, respectively.4. The image encoding method according to claim 1, wherein in a casewhere the motion picture includes a plurality of random access units,each random access unit including a plurality of pictures which arecontinuous in the decoding order, in the determining of the respectivedecoding times, the decoding time of each picture in each of the randomaccess units is determined for each of the random access units, suchthat, in each of the random access units, all the pictures except apicture to be displayed earlier in the display order than a leadingpicture in the decoding order can be decoded without referring to apicture included in another random access unit.
 5. The image encodingmethod according to claim 4, wherein the leading picture is an I picturein which a picture that is located after the leading picture in thedecoding order is prohibited from referring to a picture that is locatedbefore the leading picture in the decoding order.
 6. The image encodingmethod according to claim 4, wherein the leading picture is an I picturein which a picture that is located after the leading picture in thedecoding order and is located before the leading picture in the displayorder is permitted to refer to a picture that is located before theleading picture in the decoding order.
 7. The image encoding methodaccording to claim 1, wherein in the determining of the respectivedecoding times, in a case where a frame rate at which all the picturesincluded in the encoded motion picture are decoded and displayed is f,the decoding time of each of all the pictures is determined such thatthe decoding time of each of the plurality of lower layer picturesincluded in all the pictures is spaced apart by a time period indicatedby n times (n is an integer equal to or more than 2) a reciprocal of thef.
 8. The image encoding method according to claim 1, furthercomprising: including, into the encoded stream, display delayinformation that indicates a display delay which is a time periodbetween a decoding time of a leading picture in the decoding orderincluded in the motion picture and a display time of the leading picturein the display order included in the motion picture.
 9. The imageencoding method according to claim 1, further comprising: including,into the encoded stream, non-regular interval information that indicatesthat the determined decoding times for the plurality of picturesincluded in the motion picture are not spaced at regular intervals. 10.An image decoding method for decoding an encoded stream including amotion picture encoded for each picture which belongs to any one of aplurality of layers, without referring to another picture which belongsto a layer higher than the layer to which the picture belongs, the imagedecoding method comprising: obtaining, from the encoded stream,respective decoding times of the plurality of pictures included in theencoded stream that are determined such that decoding times of aplurality of lower layer pictures which are a portion of the pluralityof pictures included in the encoded stream and which do not belong to ahighest layer of the plurality of layers are spaced at regularintervals, and that decoding timing for each of the plurality of lowerlayer pictures is identical between a case where the plurality ofpictures included in the encoded stream are decoded and a case whereonly the plurality of lower layer pictures of the plurality of picturesare decoded; and decoding each of the plurality of pictures included inthe encoded stream or the plurality of lower layer pictures inaccordance with the obtained decoding times, wherein a display order ofthe plurality of pictures is different from a decoding order of theplurality of pictures.
 11. The image decoding method according to claim10, further comprising: changing the decoding times of each of theplurality of pictures to have the regular interval in a case wheredecoding times of the plurality of pictures included in the encodedstream are not spaced at regular intervals; and in the decoding of theencoded stream, decoding each of the plurality of pictures included inthe encoded stream or the plurality of lower layer pictures inaccordance with the changed decoding time.
 12. The image decoding methodaccording to claim 10, wherein in the decoding of the encoded stream, adetermination is made, for each picture included in the encoded stream,as to whether the decoding time obtained for the picture matchesgeneration timing at which a processing signal is generated at a certaincycle, and when the decoding time is determined to match the generationtiming, the picture is decoded.
 13. The image decoding method accordingto claim 12, further comprising determining a reciprocal of a frame rateat which all the pictures included in the encoded stream are decoded anddisplayed to be the certain cycle.
 14. An image encoding apparatus forencoding a motion picture for each picture which belongs to any one of aplurality of layers, without referring to another picture which belongsto a layer higher than the layer which the picture belongs, the imageencoding apparatus comprising: a determiner that determines respectivedecoding times of a plurality of pictures included in the motion picturesuch that decoding times of a plurality of lower layer pictures whichare a portion of the plurality of pictures included in the motionpicture and which do not belong to a highest layer of the plurality oflayers are spaced at regular intervals, and that decoding timing foreach of the plurality of lower layer pictures is identical between acase where the plurality of encoded pictures included in the motionpicture are decoded and a case where only the plurality of lower layerpictures are decoded; an encoder that encodes each of the plurality ofpictures included in the motion picture in accordance with an encodingorder according to the determined respective decoding times; and agenerator that generates an encoded stream including the plurality ofencoded pictures and the determined respective decoding times for theplurality of pictures, wherein a display order of the plurality ofpictures is different from a decoding order of the plurality ofpictures.
 15. An image decoding apparatus for decoding an encoded streamincluding a motion picture encoded for each picture which belongs to anyone of a plurality of layers, without referring to another picture whichbelongs to a layer higher than the layer which the picture in questionbelongs, the image decoding apparatus comprising: an obtainer thatobtains, from the encoded stream, respective decoding times of theplurality of pictures included in the encoded stream that are determinedsuch that decoding times of a plurality of lower layer pictures whichare a portion of the plurality of pictures included in the encodedstream and which do not belong to a highest layer of the plurality oflayers are spaced at regular intervals, and that decoding timing foreach of the plurality of lower layer pictures is identical between acase where the plurality of pictures included in the encoded stream aredecoded and a case where only the plurality of lower layer pictures ofthe plurality of pictures are decoded; and a decoder that decodes eachof the plurality of pictures included in the encoded stream or theplurality of lower layer pictures in accordance with the obtaineddecoding times, wherein a display order of the plurality of pictures isdifferent from a decoding order of the plurality of pictures.
 16. Theimage encoding method according to claim 1, wherein, the plurality ofpictures are to be decoded at the determined respective decoding times.